JPH1158634A - Soft transparent synthetic resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a synthetic resin sheet, which is harmless and no pollution is caused, by a method wherein a surface film, which is made of low density polyethylene or the like and has a specified thickness, is pasted to both the sides of a main film, which is prepared by mixing polypropylene with an amorphous polyolefin. SOLUTION: A soft transparent synthetic resin sheet is produced by pasting a main film 1 forming an intermediate layer and a surface film 2 forming a surface layer to each other. The main film is made of a composition prepared by mixing 70-50 wt.% of polypropylene with 30-50 wt.% of an amorphous polyolefin, which is obtained by copolymerizing 1-10 wt.% of ethylene, 5-30 wt.% of butene and the balancing wt.% of propylene, and has a thickness of 20-1,200 μm. In addition, the surface film 2 is made of polypropylene, low density polyethylene or straight-chain low density polyethylene and has a thickness of 5-100 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft transparent synthetic resin sheet.

[0002]

2. Description of the Related Art There are various types of synthetic resins. However, there is no resin other than a soft vinyl chloride resin capable of forming a soft and transparent film. The soft vinyl chloride resin is formed by adding a plasticizer such as dioctyl phthalate to the vinyl chloride resin.

Some films made of resins other than soft vinyl chloride resins appear to be soft and transparent.
For example, films made of polyethylene terephthalate (PET) appear to be soft and transparent. But,
This only appears to be a soft film due to the reduced thickness of the film, but is not actually soft. This is because when the PET film is bent, the bent portion is whitened or remains as a fold, and does not return completely. The same applies to films made of polyethylene and polycarbonate.

[0004] On the other hand, when a film made of a soft vinyl chloride resin is bent, the bent portion returns to its original shape without a trace. In this respect, the sheet made of a soft vinyl chloride resin is different from the other sheets made of a hard resin. Soft vinyl chloride films are unique in this regard. The softness in the present invention refers to such characteristics.

[0005] On the other hand, there is a resin other than a soft vinyl chloride resin only for producing a soft film. For example, polyolefins, especially low density polyethylene, make flexible films. However, films made of polyolefin are translucent or opaque and not transparent. Therefore, there is no resin other than the soft vinyl chloride resin that can form a soft and transparent film. Therefore, the soft vinyl chloride resin has a unique use, and is widely used as a clear holder for storing documents, a packaging film, and an agricultural film.

[0006] However, vinyl chloride resin is considered to be harmful because it contains chlorine, and when it is incinerated for disposal after use, it generates chlorine gas or hydrochloric acid gas.
This not only damages the incinerator, but also causes pollution problems. Therefore, the use of vinyl chloride resin has been avoided while being known to have excellent properties as a resin. Therefore, the appearance of a sheet made of a soft and transparent synthetic resin, such as a soft vinyl chloride resin, made of a resin other than the vinyl chloride resin is desired. Nevertheless, such sheets have not yet been made.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in response to the above-mentioned demands. That is, the sheet is essentially soft and transparent like a soft vinyl chloride resin, and is harmless when used.
An object of the present invention is to provide a synthetic resin sheet which does not cause pollution even when incinerated after use.

[0008]

Means for Solving the Problems The present inventors have found that the following improvements have been made in olefin resins. That is, polyethylene and polypropylene are essentially soft resins as described above, but because of their crystallinity, when formed into a film, they crystallize and become translucent or opaque. Therefore, recently, attempts have been made to prevent crystallization of the obtained polymer by copolymerizing ethylene or propylene with another olefin, thereby making the polymer transparent. The copolymer thus produced is sold as an amorphous olefin resin. Then, this inventor considered that the said subject was solved using such an amorphous olefin resin.

The inventor of the present invention has blended polypropylene having a low degree of polymerization with amorphous polyalphaolefin sold under the trade name "Ubetac" from Ube Lexen Co., Ltd. among olefin resins commercially available. When this is used as a composition and a film is made from this composition, the film is not completely transparent, but has a thickness of 1200 μm.
It was confirmed that if the film had a thickness of not more than m, the film would appear transparent. Therefore, when "Ubetac" was investigated, this resin was found to contain 2% by weight of ethylene and 20%.
It was found that this was an olefin-based resin having a low degree of polymerization, which was obtained by copolymerizing 1% by weight of butene-1 and 78% by weight of propylene.

Prior to the above confirmation, the inventor made a film using only the above-mentioned “Ubetak”,
It has been found that this film cannot be similar to a soft vinyl chloride resin film due to its strong adhesiveness.
Therefore, a composition was prepared by adding the same weight of polypropylene to "Ubetac", and a film was further formed from this composition. It was confirmed that the film had properties close to those of the soft vinyl chloride resin film. However, it has been found that this film still has some surface tackiness and cannot be used as a substitute for a soft vinyl chloride resin film as it is.

The inventor further conducted experiments, and as a result,
When a thin polypropylene film having a thickness of about 20 μm is attached to both sides of a film having a thickness of about 200 μm made of the above composition to form a laminated sheet, the obtained laminated sheet is close to a sheet made of a soft vinyl chloride resin. Was found. In other words, this laminated sheet has little surface adhesiveness, is transparent at all, and does not remain strongly or white even when it is creased, and can be said to be a soft and transparent synthetic resin sheet. I found something.

The inventor of the present invention has conducted further experiments,
It has been found that the films to be attached to both sides of the above-mentioned film made of the composition are not limited to polypropylene, but may be low-density polyethylene, or may be made of linear low-density polyethylene. Further, the film to be stuck on the surface is preferably thin, and the thickness is 10
It has been found that those having a thickness in the range of １００100 μm can be used. The present invention has been completed based on such knowledge.

The present invention relates to an amorphous polyolefin 3 obtained by copolymerizing 1 to 10% by weight of ethylene, 5 to 30% by weight of butene-1 and the remaining weight% of propylene.
20 to 1200 μm of a composition made by mixing 70 to 50% by weight of polypropylene with 0 to 50% by weight
m, on both sides of the film, a thickness of 5 to 5
An object of the present invention is to provide a soft transparent synthetic resin sheet obtained by laminating a 100 μm film.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partially cutaway enlarged sectional view of a soft transparent synthetic resin sheet according to the present invention. FIG. 2 is a partially cutaway enlarged sectional view of another soft transparent synthetic resin sheet according to the present invention. FIG. 3 is a partially cutaway enlarged sectional view of still another soft transparent synthetic resin sheet according to the present invention. 4 and 5 are perspective views of a clear holder and a portable toothbrush set made using the soft transparent synthetic resin sheet according to the present invention.

The soft transparent synthetic resin sheet according to the present invention is made by laminating two kinds of films as shown in FIG. Both types of films belong to the olefin-based resin, but have different compositions. One of the two films is a main film 1 forming an intermediate layer, and the other is a surface film 2 forming a surface layer. The main film 1 has a thickness greater than that of the surface film 2 and is at least twice as large as the surface film 2, preferably 5 to 20 times. Thus, the main film 1 constituting the intermediate layer
Is thicker than the surface film 2,
The main component is a soft transparent synthetic resin sheet.

The resin constituting the main film 1 is composed of an amorphous polyolefin (hereinafter referred to as APO),
This is a composition made by mixing polypropylene (hereinafter referred to as PP). Of these, APO is 1-10
By weight ethylene and 5-30% by weight butene-1;
It is an amorphous, relatively low molecular weight copolymer obtained by copolymerizing the remaining weight% of propylene. This copolymer is amorphous and thus transparent, but has a low molecular weight and thus has high tackiness, and cannot be compared to a film of a soft vinyl chloride resin as it is.

Therefore, in the present invention, it is necessary to mix APO with PP to form a composition. APO and P
The mixing ratio of P with APO is 30 to 50% by weight,
PP should be 70 to 50% by weight. APO and P
P can be originally mixed at an arbitrary ratio. AP
O is transparent as described above, but PP is translucent or opaque. Therefore, when the mixing ratio of PP is increased, the obtained composition becomes opaque. Therefore, PP needs to be 70% by weight or less. Also, APO is not suitable for forming a free-standing film because of its high tackiness as described above. Therefore, in order to suppress this stickiness, P
P needs to be added in an amount of 50% by weight or more. Thus, the mixing ratio of APO and PP needs to be the mixing ratio described above. It is preferable that the added PP has a low degree of polymerization.
It is preferably about 2 or less.

APO is commercially available as described above. For example, a product sold by Ube Lexen Co., Ltd. under the trade name of "Ubetac" corresponds to the APO referred to in the present invention. Among the products sold under the trade name "Ubetac", there are various grades, among which UT2780 is suitable.

Also, Ube Lexen Co., Ltd.
A soft polyolefin resin is sold under the trade name "AP series". Although the composition of this resin is not clear,
According to the results of the investigation by the present inventors, this resin was added to APO by PP.
Is blended. The mixing ratio of APO is 30 ~
It is estimated that PP is in the range of 70 to 50% by weight with respect to 50% by weight. Therefore, "C
“AP355Y” and “CAP330” can be used as they are to make a main film.

The resin constituting the surface film 2 is polypropylene, low density polyethylene, or linear low density polyethylene. These resins are essentially translucent to opaque. In the present invention, these resins are used to make the film as thin as possible in order to make it appear transparent. The thickness is preferably as thin as possible, but it may be necessary to increase the thickness according to another request.
Within the range. The thickness may be different between the front surface and the back surface, but is preferably the same.

As the polypropylene constituting the surface film, commercially available polypropylene can be used as it is. For example, P sold under the trade names of “Grand Polypro S-235” from Ube Industries, “Chisso Polypro 1800” from Chisso, and “J-Alomer SG-510” from Japan Polyolefin Co., Ltd.
P can be used. PP constituting the surface film
Is different from PP mixed in the main film described above, and has a high degree of polymerization.

As the low-density polyethylene (hereinafter referred to as LDPE) constituting the surface film, commercially available polyethylene can be used. For example, a product sold by Ube Industries under the trade name “F522” can be used. LDPE has a density of 0.922,
It is preferable to use one having a melt index of 5.0. Among LDPEs, in particular, linear LDPEs whose constituent molecules have no side chains (this is called LLDPE
Is preferably used. Preferred LLDPE
Has a density of 0.924 and a melt index of 1.0. For example, Ube Industries Ltd.
1A ".

If the main film 1 and the surface film 2 are made separately and are to be bonded without heating, an adhesive must be interposed between them. When glued together with an adhesive,
The resulting bonded sheet may become opaque. In order to make the bonded sheet transparent, it is suitable that the mixed resin to be the main film and the resin to be the surface film be co-extruded to form a bonded sheet. Co-extrusion is a method in which the above two types of resins are separately extruded into a single die while being melted, formed into films in the respective die, and then joined together in the same die to form a bonded sheet. It is. In this case, since the two types of resins are both olefin-based resins and have an affinity, the sheets are firmly bonded to each other without the use of an adhesive. The sheet thus obtained, of course, looks transparent.

In addition, the main film 1 and the surface film 2 can be bonded by thermocompression bonding.
The thermocompression bonding means, for example, that the surface film 2 is separately prepared in advance, the main film 1 is extruded and formed while the main film 1 is still at a high temperature and softened. This is a method in which the film 2 is attached, and the film 2 is passed between rolls and pressed and integrated.

The thickness of the surface film 2 is not more than 1/2, preferably not more than 1/5, the thickness of the main film 1. The ratio of the thickness is based on the following idea.
In other words, the surface film 2 prevents the main film from sticking and prevents the surface from being damaged.
What is originally thin is sufficient. Furthermore, since the resin constituting the surface film 2 is originally translucent or opaque as described above, the surface film 2 must be as thin as possible in order to bond it to form a transparent sheet. Must be something. Therefore, the thickness of the surface film is in the range of 10 to 100 μm in terms of absolute value.

On the other hand, since the main body film 1 forms the main body of the bonded sheet, the main body film 1 has a necessary thickness. Further, since the main film 1 is mainly composed of APO, and APO is a transparent resin, there is no problem even if the thickness is increased from the viewpoint of transparency. Generally, considering that what is called a thin sheet is about 30 μm thick and what is called a thick sheet is about 1200 μm thick, the thickness of the main film is 20 to 1200 μm. Within the range.

A flexible transparent synthetic resin sheet according to the present invention is obtained by laminating a surface film 2 on both sides of a main film 1 as shown in FIG. Among them, a sheet in which a surface film 2 having the same thickness is bonded to both sides of the main film 1 is preferable.

As shown in FIG. 2, the flexible transparent synthetic resin sheet according to the present invention is integrated with a main body film 1 and a surface film 2 with a transparent third film 3 interposed therebetween. Sheet. The third film 3 is required to be transparent. In the third film 3, the resin constituting the main film 1 is 60% by weight or more of the whole,
In particular, those having a mixing ratio of 70 to 95% by weight and the remainder consisting of the surface film 2 are preferred. The thickness of the third film 3 may be equal to or greater than the thickness of the surface film 2, but needs to be equal to or less than the thickness of the main film 1. As shown in FIG. 3, the third film 3 may be interposed between the main film 1 and the surface film 2 on both sides to form the flexible transparent synthetic resin sheet according to the present invention.

[0029]

The flexible transparent synthetic resin sheet according to the present invention has properties similar to a soft vinyl chloride resin sheet. That is, since the sheet is essentially a flexible sheet, even if it is folded or bent at a right angle to make a fold, it can be completely restored to its original flat state by returning to the original state. In other words, there is no possibility that the area around the fold will be whitened or the fold will not return to the original state even when the fold is made. Therefore, this resin sheet can be used as a material to form various objects by bending. In addition, the product made in this way is flexible and returns to its original state without being deteriorated even when bent, and has the characteristic of being beautiful because it is transparent. Thus, this resin sheet can be used to make various things that have been previously made with soft vinyl chloride resin sheets. For example, it can be used to make a clear holder (document holder) as shown in FIG. 4, a portable toothbrush set case as shown in FIG. 5, a flexible container tag, a pen case such as a ballpoint pen, a paint case, and the like. . In the case of FIG. 5, the corner portion of the case is formed by being bent at a right angle and bonded, but this is possible because of the soft sheet.

Moreover, since the sheet according to the present invention is made of an olefin resin, it can be mutually fused by heat sealing, ultrasonic processing, high frequency heating, etc., so that the secondary processing is easy. High tear resistance and excellent impact resistance. In addition, since it does not involve the problem of plasticizer extraction or the danger of chlorine gas or hydrochloric acid gas generation during incineration as in the case of soft vinyl chloride resin, it can be used as food containers and medical supplies, and after use Can be easily disposed of by incineration. Therefore, the sheet according to the present invention can be used for making food packaging, blood bags, cosmetics containers and the like. Therefore, this sheet can be expected to be widely used in fields such as office supplies, stationery, toiletries, cosmetics, clothing, bedding, medical supplies, and building materials. The present invention provides such benefits.

[Brief description of the drawings]

FIG. 1 is a partially cutaway enlarged sectional view of a soft transparent synthetic resin sheet according to the present invention.

FIG. 2 is a partially cutaway enlarged sectional view of another soft transparent synthetic resin sheet according to the present invention.

FIG. 3 is a partially cutaway enlarged sectional view of still another soft transparent synthetic resin sheet according to the present invention.

FIG. 4 is a perspective view of a clear holder made by processing a soft transparent synthetic resin sheet according to the present invention.

FIG. 5 is a perspective view of a toothbrush set case made by processing a soft transparent synthetic resin sheet according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main film 2 Surface film 3 Third film

Claims (2)

[Claims] 1 to 10% by weight of ethylene and 5 to 30% by weight.
The composition comprises a composition prepared by mixing 70 to 50% by weight of polypropylene with 30 to 50% by weight of an amorphous polyolefin obtained by copolymerizing 1% by weight of butene-1 and the remaining weight% of propylene. On both sides of a main film having a thickness of 20 to 1200 μm, a thickness of 5 to 100 made of polypropylene, low density polyethylene or linear low density polyethylene
A soft, transparent synthetic resin sheet with a μm surface film attached. 2. A transparent third film is interposed between the main film and the surface film, wherein the resin constituting the main film occupies 70 to 95% by weight of the third film, and the remaining resin forms the surface film. 2. The composition of claim 1, wherein the composition has a thickness less than the thickness of the main film.
4. The soft transparent synthetic resin sheet according to 1.).