DK143060C - Plastic bottle for liquids under gas pressure and practically resistant to deformation caused by pressure and to the penetration of gases and liquids, as well as to its process - Google Patents

Description

in 143060

The present invention relates to a plastic bottle for liquids under gas pressure and practically resistant to deformation caused by pressure and to the penetration of liquids and gases, which bottle in the unpigmented state is transparent or practically transparent and is made of ethylene terephthalate polymer or copolymer with a a glass transition temperature of at least 50 ° C, and a method of making such a bottle which is particularly useful for e.g. carbonated beverages or aerosols for which only glass bottles have so far been used.

Bottles which must be usable for carbonated beverages where there is some autogenous pressure in the bottle must possess certain necessary properties. These properties include the strength required to be able to contain beverages under pressure that can be as high as 7 kg / cm 2, with no appreciable creep or severe deformation within the temperature range of about 10 psi. o to approx. 50 * 0, which may be the case. In addition, the bottle must have no or little permeability, especially for carbon dioxide and oxygen, with a continuous loss of carbon dioxide from a carbonated beverage or the penetration of oxygen into a beverage such as e.g. beer will shorten the shelf life of the beverage and change its taste.

Heretofore, it has not been possible to replace glass bottles for gas containing liquids under pressure with plastic bottles as these have not been able to be manufactured with the above mentioned properties.

The present invention is based on the recognition that using a very special plastic material, it is possible to obtain a bottle which meets all of the above conditions, and accordingly, the plastic bottle according to the invention is characterized in that the bottle material has a logarithmic viscosity number of at least 0.55 dl / g (determined on a 1% solution of the polymer in a mixture of 37.5% by weight tetrachloroethane and 62.5% by weight phenol at 30 ° C), and that the wall of the substantially cylindrical portion of the bottle is biaxially oriented by stretching an amorphous or substantially amorphous material corresponding to a tensile ratio of not more than 4 times in the axial direction and 2.5-7 times in the circumferential direction, such that the material of this wall has a crystallinity of at least 15%, with the neck portion of the bottle consists of practically unoriented amorphous material and the bottom of the bottle is less or as sharply oriented as the cylindrical portion, the bottle being read to a thin-walled bottle to such an extent that the ratio of the bottle's weight in grams to its volume content in ml is from 0.005 to 0.2: 1 and the wall thickness of the less oriented parts is greater than the more strongly oriented parts, with the cylindrical portion of the bottle has a wall thickness of 0.25 to 0.76 mm, a tensile tensile strength in the axial direction of 350-2110 kg / cm2, a tensile tensile strength in the circumferential direction of 1400-5625 kg / cm2, an axial yield stress of at least 280 kg / cm2, a peripheral flow stress of at least 490 kg / cm2 and a deformation constant defined by the expression DC = 3 l0ga (dt / d8) Ϊ 0.65 where DC = the deformation constant, dt = the time differential, and die = the voltage differential.

The process of the invention for the preparation of this bottle is characterized in that a hollow preformed blank of any pigmented, amorphous or substantially amorphous ethylene terephthalate polymer or copolymer having a glass transition temperature of at least 50 ° C and a logarithmic viscosity number of at least 0.55 dl / g is stretched biaxially in a bottle-shaped form at a temperature of 80-130 ° C, so that the major portion of the side walls of the preformed workpiece which will constitute the generally cylindrical portion of the bottle are stretched at most 4 times in the axial direction. and 2.5-7 times in the circumferential direction to form a bottle having a weight ratio in grams to the volume in ml of between 0.005: 1 and 0.2: 1 and a crystallinity of at least 15%.

The polyethylene terephthalate bottles of the present invention have a density ranging from approx. 1,331 and 1,402, and the right cylinder portion of the bottle has, as already stated, an axial tensile strength of between about. 350 and 2,100 kg / cm 2, a peripheral tensile strength of between approx. 1,400 and 5,600 kg / cm2, an axial flow stress of at least 280 kg / cm2 and a peripheral flow stress of at least 490 kg / cm2. Typically, as already stated, these bottles will have a wall thickness of 0.25 and 0.75 mm and a deformation constant equal to the slope of the logarithm (the reciprocal value of the deformation degree) against the deformation of a value of at least about 0.65.

U.S. Patent No. 3,470,282 discloses a method of injection molding an item of polymeric material at a temperature at least equal to the melting temperature of the polymer, and cooling the melted item directly to the orientation temperature of the polymer and extending the entry in its longitudinal direction. inflated to an oriented container. Polyvinyl chloride is preferably used as polymeric material, and polyethylene, propylene and styrene are also mentioned. There is no indication that the manufactured bottles can hold liquids under gas pressure and much less that gas pressure can be maintained and diffusion prevented.

There are no indications in the patent that particular polyethylene terephthalate could be used in the known method, and no conditions are stated for the preparation of a biaxially oriented bottle of this material.

Thus, the aforementioned patent does not disclose the physical or structural properties required of a biaxially oriented polyethylene terephthalate bottle so that it can hold liquids under pressure, nor are the necessary process conditions indicated for from a preform of special polyethylene terephthalate material by blow molding can produce a bottle which, even with relatively thin walls, is so strong as to serve its purpose.

The method according to the invention is conveniently carried out by means of a mold so that the bottles can always be identical. The hollow polyethylene terephthalate exit hose is extruded through an annular nozzle into a mold having a bead recess at one end for receiving the extrudate, and then the mold is slid away from the extrusion nozzle as the continuous extrusion takes place. the extrudate is stretched while at the same time forced into the inner walls of the mold by introducing a pressurized fluid into the interior of the forming bottle.

Polyethylene terephthalates suitable for preparing the plastic bottles of the invention comprise (a) polymers of which at least approx. 97% contains recurring ethylene terephthalate units of formula o

while the remaining portion is smaller amounts of ester-forming components, and (b) copolymers of ethylene terephthalate, of which up to ca. 10 mol% consists of monomeric units such as e.g. diethylene glycol, propane-1,3-diol, butane-1,4-diol, polytetramethylene glycol, polyethylene glycol, polypropylene glycol and 1,4-hydroxymethylcyclohexane instead of the glycol molecule in the preparation of the copolymer or e.g. isophthalic acid, dibenzoic acid, naphthalene-1,4- or 2,6-dicarboxylic acid, adipic acid, sebacic acid or decane-1,10-dicarboxylic acid instead of the acid molecule part in the preparation of the copolymer.

The specific limits of the comonomer are determined by the glass transition temperature of the polymer, as it has been found that when the glass transition temperature goes below approx. 50 ° C, the result will be a copolymer with reduced mechanical properties and this corresponds to the addition of no more than approx. 10 mol% of a comonomer. An exception to this is e.g. the addition of dibenzoic acid, where the glass transition temperature of the copolymer remains above 50 ° C and does not decrease by the addition of more than 10 mol%. Other similar cases will be obvious to an expert.

In addition, the ethylene terephthalate polymer may contain various additives which do not adversely affect the polymer in use, such as stabilizers, e.g. antioxidants or ultraviolet light agents, extrusion auxiliaries, additives to make the polymer more easily degradable or combustible such as oxidation catalysts, and dyes or pigments.

As mentioned, the polyethylene terephthalate must have a logarithmic viscosity number (measured on a 1% solution of the polymer in a mixture of 37.5 wt% tetrachloroethane and 62.5 wt% phenol at 30 ° C) of at least 0.55 desired final properties of the formed bottle, and preferably the intrinsic viscosity should be at least about 0.7 to obtain a bottle with the best toughness properties, ie. resistance to impact load. The viscosity of the polymer solution is measured in relation to the viscosity of the solvent alone, and viscosity = log is obtained.

night. onion. viscosity of the solvent solvent viscosity C

where C is the concentration expressed in grams of polymer per ml. 100 ml solution.

Biaxial orientation of the bottle body is important in providing the bottles of the invention with improved physical properties such as improved tensile strength and yield strength. A biaxial orientation is obtained by stretching the thermoplastic material in the axial and peripheral directions as the article is formed. The bottle according to the invention is molecularly oriented by being stretched biaxially averaging up to 4.0 times in the axial direction and approx. 2.5-7.0 times in the peripheral direction. Such a stretch is performed at the orientation temperature of the thermoplastic material, i.e. above the glass transition temperature and below the crystal melting point. The degree of molecular orientation can be determined by known methods, e.g. as described in the Journal of Polymer Science, Vol XLVII, pages 289-306 (1960) in the article "X-Ray Determination of the Crystallite Orientation Distribution of Polyethylene Terephthalate Films" by CJ Heffelfinger and RL Burton and in "Structure and Properties of Oriented Poly (Ethylene Terephthalate) Films "by Heff elfinger and Schmidt in Journal of Applied Polymer Science, Volume 9, page 2661 (1965).

The biaxially oriented parts thus have particularly good strength properties, but the areas that are less oriented and thus weaker will have thicker wall than the areas that are more strongly oriented, and thus the bottle will have a relatively high overall strength. In the manufacture of the bottle according to the invention, the smallest wall thickness occurs in the proper cylinder part, but this part will be the most strongly oriented. In the proper cylinder portion of a polyethylene terephthalate bottle made by the process of the invention, the tensile strengths and yield stresses are typically as follows: 350-2100 kg / cm2, a peripheral tensile strength of approx. 1400-5600 kg / cm2, and an axial flow stress of at least 280 kg / cm2 and a peripheral flow stress of at least 490 kg / cm2. The tensile and yield stress values are determined by the method specified in ASTM D882 25 under "Tensile Testing".

The density (g / cm 3) of the bottle according to the invention can vary as mentioned above. 1.331 to 1.402, measured by the method described in ASTM 1505 under "Density Gradient Technique". Density is a measure of crystallinity, and the specified density range comprises a crystallinity range of from ca. 0 to 60%, with the percentage crystallinity calculated from the equation: 35% crystallinity = x 100, where Ps = density of the test sample (g / cm3)

Pa = 1.333 (g / cm3), the density of an amorphous film 7 with 0% crystallinity,

Pc = 1.455 (g / cm3), the density of the crystal calculated from unit cell parameters.

The bottles themselves may have varying crystallinity 5 along their axial length, in which case the bottle may be heat-fixed if desired to obtain uniform crystallinity.

Orientation and crystallinity each give rise to certain properties, but under some conditions they appear to be competing. Thus, e.g. Increased orientation gives increased tensile strength properties, but will tend to decrease the thermal stability of the article. To counteract this latter, the bottle can be heat-fixed to increase the crystallinity.

The crystallinity also relates to the blocking properties of the article, especially the penetration properties. When pressurized carbonated beverages such as soda or beer are bottled, it is important that the bottle has sufficient blocking properties to be able to retain the carbonic acid 20 and the water in the beverage and yet retain such contaminants as oxygen.

It has been found that an increase in crystallinity reduces the ability of carbon dioxide, oxygen or water vapor to penetrate the bottle. By the term "permeation11 and 25 its derivatives as used in the present case is meant the ability of an agent such as carbon dioxide, oxygen or water vapor to pass through or diffuse through the wall of a bottle according to the invention. The degree of permeation met using a bottle, will depend on 30 many variables, including the total surface area of the bottle, the ambient temperature, the pressure inside the bottle, as well as the type and amount of liquid in the bottle.

When the crystallinity of the bottle is at least approx. 15% (density approximately 1.348) and the bottle is used in the usual manner 35 for soda or beer in usual consumption, ie. 18, 24, 34, 36 or 48cl, the permeability rate of the 143060 δ various permeable media available is sufficient to meet commercial standards. Thus, e.g. in bottles containing up to approx. 48 cl of soda or beer under an autogenous overpressure of approx. 5.25 kg / cm 2 at room temperature, i.e. ca. And where the wall thickness is between 0.25 and 0.75 mm and the ratio between the weight in grams and the volume in cm3 is between approx. 0.2: 1 and 0.005: 1, the carbon dioxide leaving the bottle does not exceed 15% in 30 days, the oxygen penetration through the wall into the liquid will not be greater than 5 ppm in 30 days, and the amount of water lost from the liquid will not be greater than 5% in 90 days.

The carbon dioxide penetration is measured by placing a bottle under a pressure of 5.25 kg / cm2 with carbon dioxide, closing the bottle with conventional closures, placing the pressurized bottle in a vacuum chamber in which the vacuum is 1 micron Hg, and allowing the bottle into the vacuum chamber to reach equilibrium and then measure the pressure increase in the vacuum chamber as a function of time. Alternatively, the same pressurized bottle may be placed in a closed chamber with a stream of nitrogen passing through the bottle and then passed into and washed in a sodium hydroxide bath, whereupon titration of standard sodium hydroxide will indicate the amount of carbon dioxide that is occupied by passage of the nitrogen stream. The amount of carbon dioxide measured per unit of time, gives the degree of carbon dioxide penetration.

The oxygen permeation is measured by filling a bottle with degassed water, closing the bottle in the usual manner and then storing it at room temperature and pressure, periodically measuring the oxygen content of the water inside the bottle in a known manner, e.g. by potentiometric titration with silver electrode.

The water penetration is measured by placing a desiccant in a dry bottle, closing the bottle and then storing it at 37.8 ° C in an atmosphere of constant relative humidity of 100%, after which the bottle is periodically weighed to determine that of the desiccant. absorbed amount of water. Alternatively, the bottle can be filled with water, put under an autogenous overpressure of 5.25 kg / cm 2 and closed, then placed in an atmosphere of relative humidity of approx. 15% at 25 ° C and weighed at intervals to determine the water loss.

Another important feature that the bottles of the invention can be accepted for use in pressurized liquids is that they exhibit relatively low creep, especially in the case of thin-walled, low-weight bottles. Creep is the change in the structural dimension of the object that occurs upon exposure to strain, and it depends on many factors, including the load level, the nature of the polymer, the physical state of the polymer, the ambient temperature and the load time. For the creep in a regular cylindrical bottle, the size and shape of the bottle is also important. In addition, the autogenous pressure in the bottle will increase with increasing temperature and therefore the creep resistance must be relatively constant over a reasonable range of temperature and pressure. For typical applications e.g. for beer or soda, this temperature range is approx. 0-50 ° C and the pressure range is about 0-7 kg / cm 2.

The stress values that occur in a bottle used for a pressurized liquid such as a carbonated beverage are directly proportional to the autogenous pressure in the bottle and the diameter of the bottle and inversely proportional to the wall thickness. The voltage can be very closely approximated by the terms \ / peripheral ~

Vaxial ~ Pr / 2t where V = voltage P = autogenous pressure r = radius of the right cylinder t = wall thickness.

Typically, a bottle having a diameter of approx. 5 cm and a wall thickness for the right cylinder of approx. 0.50 mm to room temperature and put under an overpressure of approx. 5.25 kg / cm2 are exposed to and could withstand a peripheral voltage of approx.

143060 to 262.5 kg / cm 2 (3,750 psig).

Thin-walled bottles are desirable as this means using less polymer and making the bottle cheaper to manufacture, but thin walls lead to greater levels of tension and necessity for greater creep resistance. Bi-axial orientation of a polymer, when the other factors remain the same, will increase the yield stress of the bottle, and this is therefore an important reason for orientation.

The creep is usually measured on polymers by placing a sample under a certain load, i.e. voltage, at constant temperature, after which strain deformation is measured as a function of time. The curves for thermoplastic materials have a characteristic shape where the rate of strain decreases as a function of time. Placing the logarithm (the reciprocal value of the deformation velocity) against the voltage provides a linear course over a substantial portion of the creep curve. The slope of the straight curve piece, referred to here as the deformation constant, is expressed mathematically as DC _ d log (dt / d £) those where DC = the deformation constant dt = the time differential de = the voltage differential.

This deformation constant is applicable to related thermoplastic materials and can be used to compare the creep behavior when comparing the slope values. A deformation constant of o indicates that the specimen examined extends with its natural deformation rate or that the deformation rate at the specified load is constant. A deformation constant of infinity indicates that no measurable deformation is specified.

For bottles made according to the invention, the deformation constant is at least approx. 0.65, indicating a deformation of less than 5% in 100 hours at 50 ° C with an autogenous pressure of 5.25 kg / cm 2.

Another characteristic of the biaxially oriented polyethylene terephthalate bottles of the invention is toughness or impact resistance, but this is particularly associated with the logarithmic viscosity of the polytherephthalate, an increase of which will generally increase the impact resistance of the bottle. This is illustrated by a drop test in which a bottle is filled and closed under typical filling conditions with an autogenous overpressure of 4.2 kg / cm 2, after which the bottle 10 falls on a cement floor so that the impact point is on the edge of the base surface. When testing bottles that are manufactured in a similar manner but differ in logarithmic viscosity, it has been found that, by decreasing at 0PC, (a) bottles with a logarithmic viscosity number of 0.85 will survive a decrease of 180 cm, but fail, ie crack or break, at a fall of 240 cm, while (b) bottles with a logarithmic viscosity number of 0.95 will survive on average two falls of 240 cm, but will fail at the third fall, and (c) bottles with a logarithmic 20 viscosity numbers of 1.1 will survive five falls of 240 cm.

In the following, the method according to the invention will be explained in more detail with reference to the drawing, which shows the essential parts of an apparatus for making plastic bottles according to the invention, 1 is a cross-sectional view of the forming part of the apparatus in its position during the initial stage of forming a bottle and, in particular, the formation of the annular bead; FIG. 2 shows the same part of the apparatus in position 30 during an intermediate stage of the formation of a bottle and, in particular, the crucial step, which consists of a combination of non-melting - extrusion and expansion using internal fluid forces; FIG. 3 shows this part again, but in the position where the formation of the bottle is completed, fig. 4 shows an enlarged partial cross-section through a portion 35 of FIG. 5, namely the area around the annular extrusion nozzle near the end of the combined extrusion and expansion; and FIG. 5 is an enlarged partial sectional view similar to FIG. 6, but showing the region of the annular extrusion nozzle after the formation of the bottle is completed.

In FIG. 1, a hose 1 of polyethylene terephthalate is placed in an extrusion chamber 2 and an extrusion piston 15 is actuated to force a portion of the non-melted plastic material into the hose 1 through the annular extrusion opening 11 and into an annular groove 14 at the end. of the mold cavity 5. The purpose of this first step is to extrude an annular bead from the thermoplastic tube 1. It will be seen that the first portion of the tube 1 leaving the annular extrusion opening 11 and enters the annular groove 14 forms a bridge or diaphragm around the entire upper portion of the annular gap between the outside of the extrusion cylinder 3 and the inside of the mold cavity 5, thereby providing a closure. The extrusion of the hose into the groove 14 allows in the subsequent steps to give the extrudate axial tension by moving the mold to stretch or pull the extrudate.

Immediately after the formation of the bead in the mold cavity 5 is completed and at the same time as the continued movement of the extrusion piston 15, the mold 6 is moved at uniform speed and a fluid such as compressed air or liquid from a container is pressed into a fluid passage 8, out of fluid outlet openings. 9 and 10 and into the cavity 16 formed by the outer surface of the mandrel 7, the extruded closure at the annular groove 14 and the mold body 17 extruded through the annular extrusion opening 11 and expanded by the compressed air from the output openings 9 and 10. This is shown in FIG. Third

Hereby, as the mold 16 moves relative to the opening 11, the bead formed in the annular groove 14 will anchor the newly formed bottle top to the mold 6 and effectively move the fresh extrudate past the compressed air flowing out of the outlet openings 9 and 10, causing this extrudate to be forced almost immediately against the wall of the mold cavity 5 as it emerges from the opening 11.

In the presently preferred method, a plastic bottle of non-uniform wall thickness is produced because the extrusion rate and the velocity of the mold are kept constant while the mold itself has varying shapes. However, it is well known that the wall thickness can be regulated by proper programming of the apparatus to obtain either a uniform or a non-uniform thickness. Known methods for programming the wall thickness include varying the speed of the sliding mold or varying the extrusion speed of the hose.

The thermoplastic polymeric material in the tube 1 extruded through the annular extrusion opening 11 is biaxially oriented partially by the extrusion operation itself, while the other portion of the desired biaxial orientation of the extruded mold body 17 occurs as the extrudate is stretched and expanded. towards the surface of the mold cavity 5 in the mold 6. A substantial reduction is seen, e.g. up to 50% or more, of the wall thickness of the extrudate after it is stretched and expanded.

The hose 1 continues to be extruded through the annular extrusion opening 11 of the extrusion piston 15, while the mold 6 moves toward its second position above the mandrel 7. The overall effect of the extrusion of the hose 1 and the expansion 16 results in the desired shape of the . 3, but it still has a closed bottom portion as best seen in FIG. 4. The bottom portion of the bottle 18 is closed by removing the supporting center bar 4 while the mold 6 stops and the extrusion piston 15 continues to exert a force on the remaining polymeric material in the extrusion chamber 2. This is shown in FIG. 3 14 1460 with the finished bottle 19, which is in a strongly biaxially oriented state.

FIG. 4 and 5 show in more detail the preferred way of bottom closure, where the partial removal of the center bar 4 allows polymeric material in the tubing during the continued pressing of the extrusion piston 15 to flow inward and effect a closure. Alternatively, the bottom may be closed in the manner described in U.S. Patent Application No. 57,679 of July 23, 1970, wherein a friction welded bottom closure of a plastic bottle is effected by bringing the bottom of the bottle into the area adjacent to the bottom opening. contact with a friction closure head to raise the temperature of the thermoplastic material to approx. its melting point, after which the hot thermoplastic material is incorporated into and welded into the bottom orifice, whereupon the closed orifice is quenched. This method can be carried out while the bottle is still in the mold, or as a separate operation after the bottle is removed from the mold.

FIG. 5 shows the position of the parts of the apparatus after the completion of the method of forming a hollow article from a hollow hose. In FIG. 5, the center rod 4 has been removed, while the extrusion piston 15 presses the remaining portion of the thermoplastic tube 1 into the space which has become vacant by retraction of the rod 4.

After forming the thermoplastic bottle, it can be heat-treated according to known methods of increasing the degree of crystallinity, thereby reducing the ability of gases to penetrate the wall and improving dimensional stability, which is important if the article is used for hot drinks or must be exposed to high temperatures and pressures in a pasteurization process.

The heat treatment is carried out at temperatures of between approx. 140 and 220 ° C and the treatment time is relatively short. However, it is generally desirable to carry out the heat treatment over a period of time sufficient to give in the finished product a degree of crystallinity which is preferably at least approx. 30% and up to 50% or more, with the maximum achievable crystallization for polyethylene terephthalate being approx. 60%. Generally, particularly good results have been observed when this heat treatment step is carried out over a period of between approx. 0.1 and 600 seconds. The upper limit of this treatment is not very critical, except from an economic point of view, and a duration of up to 100 minutes of treatment is possible.

The thermoplastic tube used for the method of the invention is hollow, but hereby, unless otherwise indicated, a tube-like tube with both ends is open as well as a tube-like tube with one end open and the other closed, i.e. a "blind" hose, the latter being positioned in the extrusion cylinder such that the closed end will form the bottom of the bottle. The tube-like hose with both ends open can be used with the apparatus comprising a stationary center bar or movable center bar, while a "blind" hose can only be used with the apparatus including a movable center bar.

The hose is preferably manufactured by conventional extrusion or injection molding methods from thermoplastic materials which can be imparted to increased strength or reinforcement by biaxial orientation. The hose itself may be biaxially oriented or unoriented prior to use. If an oriented hose is used, the additional orientation that occurs during extrusion, drawing and expansion of the extruded hose will give an additive effect. In addition, the tube should be practically amorphous with a crystallinity of no more than ca. 5% and it should be ready as this will result in a clear finished bottle. However, if it is desired for the bottle to be colored, a coloring agent such as a dye may be added to the tubular polymer.

The dimensions of the tubing to be used are determined by many factors, including the desired thickness and degree of orientation. Typically, the tube is hollow, and the radial dimensions are slightly smaller than that of the neck of the bottle to be made as shown in the drawing. The axial length of the hose is slightly shorter than the dimension between the top and bottom center, measured along the outside of the bottle to be manufactured. To improve the dimensional stability of the bottle, especially the radial dimensions of the bottle neck, the hose is first formed with radial dimensions of substantial oversize, then quenched to a temperature below the crystalline melting point of the polymer and then pressed through a thickness-reducing nozzle slightly smaller than those of the bottle. desired radial dimensions for the bottleneck as shown in the drawing. To further improve dimensional stability, the tube may be compressed into a chamber which maintains the same outside diameter with a tapered mandrel in the center of the compression chamber, which will result in a very short tube with an outside diameter having a slightly smaller size than the one. outside diameter of the bottleneck, and an inside diameter of practically 0, which will result in a very narrow cavity of approx. the same size as a pinhole that runs through the center of the hose. Compressed hoses are used in the apparatus described above without the presence of the center bar or with this fully retracted.

The reason why the material used is polyethylene terephthalate is that, by orientation, it exhibits excellent strength, creep resistance and low penetration factor, especially with respect to carbon dioxide, oxygen and water vapor, making it excellent for containers for pressurized liquids such as sodas, beer or aerosols. It is advantageous to assume practically amorphous material, ie. a crystallinity of not more than 5%, to obtain a clear bottle. Applicable polyethylene terephthalate polymers have a logarithmic viscosity number of at least 0.55, measured for a polymer concentration of 1% in a 37.5 / 62.5 wt% solution of tetrachloroethane / phenol at 30 ° C. Preferably, the viscosity number is at least 0.7, thereby providing a bottle with significantly improved toughness properties, e.g. increased impact resistance.

Impact resistance is measured by dropping a hose onto a concrete floor from different heights. In a drop test carried out on 15 cm long tubes of amorphous polyethylene terephthalate with an intrinsic viscosity of approx. 1.1 where three tubes were used for testing with an average wall thickness of approx. 3.5, 2.3 and 2.4 mm and weighing 27.8 g, 21.2 g and 21.6 g respectively, each hose withstood two falls from a height of 0.3, 0.6, 1 , 5 and 2.40 m without any visible damage to the hose, and in addition, each hose withstood the weight of 2.27 kg, which fell twice on the hose from a height of 0.3 m.

Bottles with laminated walls can be made by the method of the invention using a hollow cylinder tube with laminate walls which can be obtained by coaxial lamination of two or more tubes of identical or different materials. Examples of practically useful combinations are polyethylene terephthalate on the inside coaxially laminated to polyvinylidene chloride copolymer or hydrolyzed ethylene vinyl acetate copolymer on the outside. Hoses of multiple polymeric materials can be extruded simultaneously in two or more layers, viz. preferably in three layers, with the additional polymer interposed between the polymer base or bottle formation layers. Using such a hose, it is possible to produce bottles of base resins with a selected laminate that can be used as (1) gas barriers, (2) staining layers, or (3) degradation catalyst.

The extruded tube must have a temperature within the range of biaxial orientation, i.e. the temperature range of the polymer used, in which a non-line orientation can occur. The heat generated during the extrusion is generally sufficient for this purpose so that the tubing can be extruded at room temperature, but the orientation temperature range varies from polymer to polymer depending on such factors as crystallinity and the glass transition temperature of the polymer and if the orientation region of the polymer is so high that the extrusion heat is not sufficient to raise the polymer temperature to the orientation region, the hose can be preheated before the extrusion.

The plastic bottle formed is biaxially oriented and will have physical properties according to the type of hose used.

The following examples are intended to further illustrate the invention.

Example 1

Of a polyethylene terephthalate polymer having a logarithmic viscosity number of approx. 0.96, a hollow, cylindrical, amorphous shaped tube having a length of 11.4 cm, an outside diameter (out) of 1.73 cm and an inside diameter (id) of 0.95 cm is produced, and weighs approx. 22.6 g. This hose is preheated to approx. 92 ° C and extruded through an opening "T" of approx. 0.84 mm at a cylinder temperature of approx. 85 ° C in the apparatus described above. The speed of the extrusion piston 15 is approx. 9.1 cm / sec and the speed of the mold 6 is approx. 13.0 cm / sec. Air with an overpressure of approx. 17.85 kg / cm 2 is inserted through the openings 9 and 10 and the internal diameter of the mold is approx. 6.4 cm.

A bottle with a wall thickness of approx. 0.30 mm and its axial tensile strength is approx. 1,155 kg / cm 2, while the peripheral tensile strength is approx. 1.869 kg / cm2.

Example 2

Example 1 is repeated with the following data.

1.0

16.5 cm 17.3 mm 12.1 mm 23.5 g 100eC

Viscosity number, log Hose length Hose diameter, outside Hose diameter, inside Hose weight Preheating temp.

19 143060

Cylinder temp. Opening "T" Piston speed Shape speed Air pressure Tensile strength, axial Tensile strength, peripheral Wall thickness 90-100 ° C 0.89 mm 12.7 cm / sec. 14.7 cm / sec. 245 kg / cm 2 2,560 kg / cm 2 2.121 kg / cm 2 0.43 mm

Example 3

A plastic bottle is prepared in the same manner as in Example 1 by extrusion and blow molding a hollow cylindrical shaped tube having a length of 11.4 cm, an outside diameter of 17.3 mm and an inside diameter of 9.5 · mm. and weighing approx. 22.6 g. The tube is prepared from a polyethylene terephthalate having a logarithmic viscosity number of 0.91, and the tube has a density at the outer surface of 1.332 and at the inner surface of 1.334, and a crystallinity of approx. 5%.

The bottle thus produced exhibits the following properties: In density and crystallinity of polymer from different locations on the bottle

Lot-

Crystal lineage fullness

The neck The upper part of the cylinder part The middle of the cylinder part The bottom of the cylinder part Bottle bottom 1,332 1,345 1,356 '1,361 1,332 0 6 17 22 0 20143060

II Strength Properties (The Right CvlinderdeH

Tensile strength, kg / cm2 Extension,% Tensile modulus, kg / cm2 Flow stress, kg / cm2

Axial Peripheral 546 1,666 59 17 17,220 47,810 532 700 III Biaxial Orientation X-ray orientation angles according to the articles previously referred to 20 Θ tip Rotational direction Orientation Tip x (chi) <p (phi) angle max. 17.0 Plan perpendicular to beam 83 (axial) 0 ° X Plan parallel to beam Scan 90 52 (peripheral) 0 ° X 0 Scan 66 (peripheral) 0 ° X 27.0 Plan perpendicular to beam Scan 0 - - Plan parallel to the beam Scan 90 32 (peripheral) 5 ° X 0 Scan 40 (peripheral) 87 ° 0

From the above X-ray orientation angles and strength properties, it is seen that the bottle exhibits an effective stretching ratio of approx. 3.5 times in the circumferential direction and approx. 1.25 times in the axial direction.

IV Permeability of the right cylindrical part Wall thickness 0.46 mm

Water loss 0.6 mg / hour (Bottle filled with water and stored at a relative humidity of 17.5% and 25 ° C for 13 days) 21143060 1/5 cm3 / day (s tandard temperature and pressure)

Carbon dioxide loss (The bottle is pressurized with carbon dioxide to an excess pressure of 2.8 kg / cm2 at 25 ° C. The bottle shows no permanent deformation) V Requirements

Circumference strips from the right cylinder portion of a sacrificed bottle withstand a peripheral tensile stress of 350 kg / cm2 at 50 ° C with a creep of 100 hours of value less than 2% and a long-term creep of 90 days of less than 5%, which corresponds to a deformation constant of approx. 1.5.

Claims (2)

143060 Patent Claims. 1. Plastic bottle for liquids under gas pressure and practically resistant to deformation caused by pressure and to the penetration of liquids and gases, which bottle in the unpigmented state is transparent or practically transparent and is made of ethylene terephthalate polymer or copolymer with a glass transition temperature at least 50 ° C, characterized in that the bottle material has a logarithmic viscosity number of at least 0.55 dl / g (determined on a 1% solution of the polymer in a mixture of 37.5% by weight tetrachloroethane and 62.5% by weight phenol at 30 ° C) and the wall of the substantially cylindrical portion of the bottle is biaxially oriented by stretching an amorphous or substantially amorphous material corresponding to a tensile ratio of at most 4 times in the axial direction and 2.5-7 times in the circumferential direction, thus that the material of this wall has a crystallinity of at least 15%, the neck portion of the bottle consisting of substantially unoriented amorphous material, and bottle n's bottom is less or as strongly oriented as the cylindrical portion, the bottle being inflated to a thin-walled bottle such that the ratio of the bottle's weight in grams to its volume content in ml is from 0.005 to 0.2: 1, and the wall thickness of the less oriented parts is greater than the more strongly oriented parts, the cylindrical portion of the bottle having a wall thickness from 0.25 to 0.76 mm, a tensile strength in the axial direction of 350-2110 kg / cm2, a tensile strength in the circumferential direction of 1400-5625 kg / cm2, an axial flow stress of at least 280 kg / cm2, a peripheral flow stress of at least 490 kg / cm2, and a deformation constant defined by the term d log (dt / die) DC = -> 0.65 die where DC = the deformation constant, dt = the time differential, and die = the voltage differential. 143060 Process for producing a thin-walled plastic bottle as claimed in claim 1, characterized in that a hollow preformed blank of any pigmented, amorphous or substantially amorphous ethylene terephthalate polymer 5 or copolymer having a glass transition temperature of at least 50 ° C and a logarithmic viscosity numbers of at least 0.55 dl / g are stretched biaxially in a bottle-shaped mold at a temperature of 80-130 ° 0, so that the majority of the side walls of the preformed blanket are generally cylindrical in the bottle. part, is stretched a maximum of 4 times in the axial direction and 2.5-7 times in the circumferential direction to form a bottle having a weight ratio in grams to the volume in ml of between 0.005: 1 and 0.2: 1 and a crystallinity of at least 15%.