JP3345093B2 - Method for producing polyolefin resin foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a carbon dioxide
Polypropylene using inorganic gas containing carbon or carbon dioxide
The present invention relates to a method for producing a pyrene- based resin foam.

[0002]

2. Description of the Related Art A foaming agent is usually used for producing a polyolefin resin foam. As the blowing agent, a pyrolytic organic blowing agent such as azodicarbonamide, a low-boiling organic solvent blowing agent such as pentane and dichlorodifluoroethane, and an inorganic gas blowing agent such as carbon dioxide and nitrogen are used.

[0003] In the case of using a thermally decomposable organic foaming agent, since the foam contains decomposition residues of the foaming agent, discoloration and odor are generated in the foam and the quality is deteriorated. When a low-boiling organic solvent blowing agent is used, there are environmental problems such as danger of explosion and destruction of the ozone layer. The use of an inorganic gas blowing agent is preferable because the above-described problems do not occur and the cost is low.

However, when polyolefin resin is extruded and foamed using an inorganic gas as a foaming agent, the inorganic gas has poor compatibility with the resin, and separates quickly from the resin during foaming.
For this reason, it is difficult to have uniform and fine air bubbles and foam at a high magnification (for example, 10 times or more).

In order to generate uniform and fine bubbles, a bubble nucleating agent such as calcium carbonate or talc is usually used. Of course, the viscoelasticity of the resin and the amount of press-fit of the inorganic gas are also adjusted (for example, see Japanese Patent Publication No. 60-26418).

[0006]

[Problems to be solved by the invention]

However, the inorganic gas does not have the effect of removing latent heat of evaporation from the resin when the resin is foamed and fixing the bubbles. In addition, when a large amount of the bubble nucleating agent is used, the elongation of the resin becomes poor. Therefore, when an inorganic gas is injected into the resin at a high pressure to obtain a high magnification, bubbles are easily broken,
The foaming ratio is at most about 8 times, and it is not easy to foam at a higher ratio.

[0008] The present invention is intended to solve the above problems, it is an object of carbon dioxide given as blowing agent
Or long-chain branching using inorganic gas containing carbon dioxide
The present invention provides a method for producing a polypropylene resin foam having uniform and fine cells, a high closed cell rate, and easy foaming at a high magnification.

[0009]

In the present invention , the resin is a polypropylene resin having a long chain branch (polypropylene resin).
Propylene and propylene copolymer) .

The polypropylene resin having a long chain branch preferably has a melt index (MI) of 0.05 to 20 according to JIS K7210. If the MI of the resin is too low, the melt viscosity becomes high and not only a high magnification foam cannot be obtained, but also the load on the extruder increases and extrusion becomes difficult. Conversely, if the MI is too high, the foam has a low viscosity with respect to the elongation of the resin at the time of foaming, so that the foam tends to be broken, and a foam having a high magnification cannot be obtained.

[0011] Polypropylene resins (polypropylene and propylene copolymers) having long chain branches are preferred because of their excellent heat resistance and mechanical strength .

A polypropylene resin having a long chain branch has a higher melt tension (elongational viscosity) than a conventional polypropylene resin having no long chain branch. Therefore, when a polypropylene resin having such a long chain branch is used, the viscosity, tension and elongation at the time of melting are suitable for foaming, and the suitable foaming temperature range is widened.

Particularly, in a polypropylene resin having a long chain branch, the elongation strain rate is 0.01 to 1.0 (s ^-1 ).
Elongation strain amount A at any two points that can be measured within the range of
B, the respective melt extensional viscosities η _A (Pa ·
s), the maximum value of the ratio of η _B (Pa · s) is η _B / η _A =
3.0-100, and B / A = 10, A = 0.1-1.
Those which are 0 are preferred.

Incidentally, the η _B / η _A of a conventional polypropylene resin having no long-chain branch is generally 2.0 or less.
The melt extensional viscosity of the resin can be easily measured using a commercially available melt extensional viscometer (for example, a melten rheometer manufactured by Toyo Seiki Co., Ltd.).

In the present invention, first, the above-mentioned long-chain branch is provided.
An inorganic cell nucleating agent surface-treated with a coupling agent is mixed with the polypropylene resin to be prepared to prepare a resin composition. Here, as the inorganic cell nucleating agent, an inorganic cell nucleating agent conventionally used for producing a foam is used.

Examples of these cell nucleating agents include talc,
Calcium carbonate, clay, kaolin, mica, magnesium oxide, zinc oxide, carbon black, glass, quartz,
Examples thereof include silica, alumina, novaculite, hydrated alumina, wollastonite, iron, iron oxide, silicon dioxide, and titanium oxide.

These bubble nucleating agents preferably have an average particle size of 0.1 to 500 μm, more preferably 1 to 500 μm.
100 μm. If the average particle size is too large, the cell diameter of the obtained foam becomes coarse, and the surface smoothness and the heat insulating property decrease.Conversely, if the average particle size is too small, it becomes difficult to uniformly disperse the resin, A foam with uniform and fine cells cannot be obtained.

As the coupling agent for treating the surface of the cell nucleating agent, a silane coupling agent or a titanate titanium coupling agent is mainly used. In addition, an aluminum coupling agent or a zirconia coupling agent is used. Agents and the like can also be used.

These coupling agents have, in the molecule, a group having reactivity or affinity with an inorganic substance and a group having reactivity or affinity with an organic substance. In particular, the group having reactivity or affinity with an inorganic substance is preferably an alkoxy group or a hydroxyl group, and the group having reactivity or affinity with an organic substance is preferably a vinyl group, a phenyl group, an alkyl group, or a (meth) acrylic group. Groups are preferable, and a glycidyl group, an amino group, a mercapto group, or the like may further be present in these groups.

In the example of the silane coupling agent, 3-
[N-allyl-N (2-aminoethyl)] aminopropyltrimethoxysilane, 3- [N-allyl-N-glycidyl) aminopropyltrimethoxysilane, 3- [N-
Allyl-N-methacryl) aminopropyltrimethoxysilane, p- [N- (2-aminoethyl) aminomethyl] phenethyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, 3
-Aminopropyltriethoxysilane, N, N-bis [(methyldimethoxysilyl) propyl] amine,
N-bis [3- (methyldimethoxysilyl) propyl]
Ethylenediamine, N, N-bis [(methyldimethoxysilyl) propyl] methacrylamide, N, N-bis [3- (trimethoxysilyl) propyl] amine,
N-bis [3- (trimethoxysilyl) propyl] ethylenediamine, N, N-bis [3- (trimethoxysilyl) propyl] methacrylamide, cyclohexylmethyldimethoxysilane, 3- (N, N-diglycidyl) aminopropyltripropyl Methoxysilane, dimethyldiethoxysilane, dimethyldimethoxysilane, dimethylethoxysilane, dimethylvinylethoxysilane, dimethylvinylmethoxysilane, diphenyldiethoxysilane, diphenyldimethoxysilane, diphenylsilanediol,
N-glycidyl-N, N-bis [3- (methyldimethoxysilyl) propyl] amine, N-glycidyl-N, N
-Bis [3- (trimethoxysilyl) propyl] amine, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, hexyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-methacrylic Roxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, methyltrimethoxysilane, methyldiethoxysilane, methyldimethoxysilane, methyltris (dimethylsiloxy) silane, methylvinyldiethoxysilane, methylvinyldimethoxysilane, octadecylmethyldimethoxy Silane, octadecyltriethoxysilane, octadecyltrimethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, N-
[(3-trimethoxysilyl) propyl] diethylenetriamine, N-[(3-trimethoxysilyl) propyl] triethylenetetramine, N-3-trimethoxysilylpropyl-m-phenylenediamine, trimethylsilylvinylbicyclo [2.2. 1] heplan, trimethylmethoxysilane, triphenylethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, vinyltrimethoxysilane, β-
(3,4-epoxycyclohexyl) ethyltrimethoxysilane and the like.

Examples of the titanate-based coupling agent include isopropyl triisostearoyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (N-aminoethyl-aminoethyl) titanate, and tetraoctyl bis (ditridecyl phosphite) titanate. , Bis (dioctyl pyrophosphate) oxyacetate titanate, bis (dioctyl pyrophosphate) ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri ( Dioctyl phosphate) titanate, isopropyl tricumyl Eniruchitaneto, tetraisopropyl bis (dioctyl phosphite) titanate.

Examples of the aluminum-based coupling agent include acetoalkoxyaluminum diisopropylate.

In order to treat the surface of the above-mentioned bubble nucleating agent with a coupling agent, for example, the coupling agent is dissolved in water or an organic solvent such as alcohol, hexane, toluene, etc. A method of removing water or an organic solvent by mixing and stirring the agent with a Henschel mixer or a super mixer, followed by heating and drying is adopted.

Alternatively, a method of spraying a coupling agent solution with dry air or nitrogen gas while forcibly stirring the bubble nucleating agent with a V blender, or a method of heating the bubble nucleating agent and coupling it in a high temperature state A method of spraying an agent solution can also be adopted.

In this case, the surface treatment is preferably carried out at a ratio of 0.1 to 10 parts by weight of the coupling agent to 100 parts by weight of the cell nucleating agent. If the surface treatment amount of the coupling agent is too small, the surface of the cell nucleating agent is incompletely treated,
The affinity between the resin and the cell nucleating agent is inferior, and outgassing during extrusion foaming increases, making it difficult to foam at high magnification. Conversely, if the surface treatment amount of the coupling agent is too large,
It is useless because the effect proportional to the surface treatment amount does not increase.

The inorganic cell nucleating agent surface-treated with the above coupling agent is used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the polypropylene resin having a long chain branch. It is preferably contained. If the content of the surface-treated cell nucleating agent is too small, the foam of the obtained foam will be coarse, and conversely, if the content of the surface-treated cell nucleating agent is too large, the elongation of the resin during foaming will increase. It becomes worse and easily breaks, making it difficult to foam at a high magnification.

Next, a resin composition containing a surface-treated cell nucleating agent in a polypropylene resin having a long chain branch is extruded using carbon dioxide or an inorganic gas containing carbon dioxide as a foaming agent. Let it foam. In general, a vent-type extruder is used for extrusion foaming of the resin composition, and a carbon dioxide gas or a carbon dioxide gas is contained as a foaming agent in the melt-kneaded resin composition in the extruder from a vent portion of the extruder. <br/> Inorganic gas is injected.

In addition, the raw material supply port of the extruder is sealed, and carbon dioxide or carbon dioxide gas is contained from the raw material supply port .
Pressurized inorganic gas into the resin, using a perforated extrusion screw , containing carbon dioxide or carbon dioxide through the holes
A method of press-injecting an inorganic gas into the resin may be employed.

In the present invention, carbon dioxide has a long-chain branch.
High solubility in polypropylene resin
As a foaming agent, carbon dioxide or nitrogen containing carbon dioxide can be used.
Containing air, oxygen, neon, inorganic gas such as argon using
Can be

These carbon dioxide or carbon dioxide containing
The amount of inorganic gas used (injection amount) depends on the type and length of inorganic gas.
Depending on the type of the polypropylene resin having a chain branch and the desired expansion ratio, the injection pressure is generally from 25 to 150 kg, as indicated by a pressure gauge attached to the injection section of the extruder.
/ Cm ² .

If the amount of the carbon dioxide gas or the inorganic gas containing the carbon dioxide gas is too small, the gas expansion pressure at the time of foaming is too small to obtain a uniform and fine cell foam. Conversely, if the amount of the inorganic gas used is too large, the expansion pressure of the gas at the time of foaming increases, the cell membrane ruptures, the surface properties deteriorate, and a high-magnification foam cannot be obtained.

The molten resin composition into which carbon dioxide or an inorganic gas containing carbon dioxide is injected is continuously extruded into a desired shape from a die of an extrusion die provided at the tip of an extruder. Is opened to foam the resin composition. The shape of the die of the extrusion die is generally similar to the shape of the target foam.

The temperature of the resin composition extruded from the die is preferably adjusted within the range of the melting point of the resin ± 10 ° C. When the temperature of the resin composition is too low, the viscosity of the resin is too high to make extrusion difficult.On the contrary, when the temperature of the resin composition is too high, the viscoelasticity of the resin becomes low and the foam easily breaks, It becomes difficult to foam at a high magnification.

In this way, the resin composition extruded from the extrusion die is foamed well, has uniform and fine cells, and has a closed-celled long-chain branched foam which has been expanded at a high magnification.
A len- based resin foam is manufactured. The foam of the resin composition extruded from the extrusion die is preferably cooled with water, cold air, or the like in order to keep the shape of the foam.

In addition, as long as the effects of the present invention are not impaired, additives such as a flame retardant, a filler, an antioxidant, a flame retardant, and a pigment may be added to the polypropylene resin having a long chain branch. May be blended. Such additives are widely known.

Examples of the flame retardant include brominated flame retardants such as hexabromobiphenol ether and decabromodiphenyl ether, phosphorus-containing flame retardants such as ammonium polyphosphate, trimethyl phosphate and triethyl phosphate, melamine derivatives, inorganic flame retardants and the like. There is.

[0037]

[Function] By supplying an extruder with an inorganic bubble nucleating agent and an inorganic gas, which are surface-treated with a polypropylene resin having a long chain branch and a coupling agent, and foaming the resin, the affinity between the resin and the coupling agent increases. Containing carbon dioxide or carbon dioxide
The separation of the inorganic gas from the resin is suppressed quickly.

Therefore, even if a bubble nucleating agent is used to generate uniform and fine bubbles, carbon dioxide or carbon dioxide can be used.
Inorganic gas containing acid gas fraction escaping from the resin is reduced before contributing to the foaming, with the formation of uniform fine bubbles with a small amount of the bubble nucleating agent takes place, some carbon dioxide
Alternatively, an inorganic gas containing carbon dioxide is efficiently used for foaming the resin, and the resin foams at a high magnification.

[0039]

EXAMPLES Examples and comparative examples of the present invention will be described below. Example 1 1 part by weight of 3-methacryloxypropyltrimethoxysilane was added to 3 parts by weight of a mixed solution of ethanol and water (containing 80% by weight of ethanol) and mixed to prepare a silane coupling agent solution.

100 parts by weight of talc (MS: manufactured by Nippon Talc) having an average particle size of 9 μm are charged into a supermixer and, while stirring, 4 parts by weight of the above silane coupling agent solution are divided into several portions and mixed for several minutes. And stirred with a super mixer for another 7 minutes, then removed to a tray for 150 minutes.
After drying at ℃ for 1 hour, talc A treated with a coupling agent was prepared.

Polypropylene (MI4, melting point 169 ° C.)
(Pro-fax PF814: HIMONT, USA)
Ltd.) to 100 parts by weight, the coupling agent-treated talc A0.
The resin composition was prepared by mixing 6 parts by weight, and the resin composition was supplied from a hopper of a vent type extruder (65 mm in diameter, L / D = 35) set at a temperature of 130 ° C. to the extruder as a raw material. The mixture was supplied to the mouth, and the resin composition was melt-kneaded in an extruder.

The above polypropylene had a long-chain branch, and the measured values of the melt extensional viscosity were as follows. Elongation strain rate: 0.4 s ^-1 elongation strain amount A: 0.86, elongation strain amount B: 8.6, melt elongation viscosity η _A : 21544 Pa
S, melt extension viscosity η _B : 843190 Pa · s, η _B
/ Η _A : 39.1. Here, the melt elongation viscosity was measured using a Melten rheometer (manufactured by Toyo Seiki Co., Ltd.).

[0043] Then, the carbon dioxide gas from the vent of the extruder was injected at a pressure of 75 kg / cm ^2, which was melt-kneaded in an extruder, and 20 from an extrusion die of the subsequent set 2mm diameter to 108 ° C. Extrusion foaming was performed at an extrusion rate of KG / hr to continuously produce a rod-shaped foam.

The expansion ratio of the resulting foam is 20.8 cc /
g, closed cell ratio is 77.7 %, average cell diameter is 390 μm
Thus, the foam was foamed at a high magnification with uniform fine cells and a high closed cell ratio. The closed cell ratio was measured using an air-comparison hydrometer 1000 (manufactured by Tokyo Science). The results are summarized in Table 1.

[0045] In Comparative Example 1 Example 1, polypropylene (MI 4, melting point 16
9 ° C.) (Pro-fax PF814: HIMON, USA)
T) and low density polyethylene A (MI2.
8, melting point 112.5 ° C) (Yukaron ZH51, Mitsubishi Yuka)
And no talc A treated with a coupling agent. Other than that, it carried out similarly to Example 1. The results are summarized in Table 1.

[0046] In Comparative Example 2 Example 1, polypropylene (MI 4, melting point 16
9 ° C.) (Pro-fax PF814: HIMON, USA)
T) and low density polyethylene A (MI2.
8, melting point 112.5 ° C) (Yukaron ZH51, Mitsubishi Yuka)
Co., Ltd.) and replace the coupling agent treated talc A with
0.6 parts by weight of talc not treated with a coupling agent (untreated talc) was mixed. Other than that, it carried out similarly to Example 1. The results are summarized in Table 1.

[0047]

[Table 1]

[0048]

As described above, the present invention has a long-chain branch.
Containing a foamed polypropylene resin, an inorganic cell nucleating agent surface-treated with a coupling agent, and carbon dioxide or carbon dioxide.
With an inorganic gas that has been supplied to the extruder and foamed,
As a result, the foaming properties of the resin by carbon dioxide gas or an inorganic gas blowing agent containing carbon dioxide gas are improved, and uniform and fine bubbles are obtained, and the closed cell ratio is high, and the polypowder foamed at high magnification.
A pyrene- based resin foam can be easily obtained.

Further , according to the present invention, charcoal is used as a foaming agent.
Uses an inorganic gas containing an acid gas or a carbon dioxide gas, so it is inexpensive and does not cause explosion danger or environmental problems, and the resulting foam does not generate discoloration or odor and does not deteriorate in quality There is an advantage.

[0050] Then, according to the present invention, films, sheets, boards, tubular, various shapes of the rod-shaped like a long poly
A propylene- based resin foam is obtained, and can be used for a wide variety of uses such as a heat insulating material, a cushioning material, a soundproofing material, a float, and a sealing material.

Claims (1)

(57) [Claims] An inorganic cell nucleating agent surface-treated with a coupling agent and a polypropylene resin having a long chain branch.
A method for producing a polypropylene- based resin foam, characterized in that carbon dioxide or an inorganic gas containing carbon dioxide is supplied to an extruder and foamed.