JPH0711038A - Foamable resin composition - Google Patents

Abstract

PURPOSE:To obtain a foamable resin composition extremely reduced in the destruction of the ozonosphere and capable of stably giving foamed products containing uniform and fine closed pores having a high foaming ratio and free from discoloration and smell. CONSTITUTION:This foamable resin composition comprises 100 pts.wt. of a thermoplastic resin, 0.1-10 pts.wt. of a water-absorbable substance, 0.1-2 pts.wt. of water and 0.1-10 pts.wt. of 1,1,1,2-tetrafluoroethane, or comprises 100 pts.wt. of the thermoplastic resin, 0.1-5 pts.wt. of an alcohol, and 0.1-10 pts.wt. of the 1,1,1,2-tetrafluoroethane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamable resin composition for obtaining a foam having high quality and high magnification with extremely low ozone depletion.

[0002]

2. Description of the Related Art A method for producing a polyolefin resin foam having uniform and fine closed cells at a high magnification is known by injecting water when the polyolefin resin is extruded and foamed by using a foaming agent ( For example, Japanese Patent Publication Sho 52
-20500).

In the above method, when a fluorine-containing low boiling point organic compound is used as the foaming agent, it is nonflammable and nontoxic, and the decomposition residue of the foaming agent is contained in the foam like a decomposable organic foaming agent. Therefore, there is an advantage that the foam does not cause discoloration or odor.

Dichlorotetrafluoroethane (CFC 114) and dichlorodifluoromethane (CFC 12) have been widely used as the above-mentioned fluorine-containing low boiling point organic compounds. However, these fluorine-containing low boiling point organic compounds have an extremely large environmental depletion due to the great destruction of the ozone layer in the atmosphere.

In recent years, ozone depletion is extremely small, and 1,1,1,2-tetrafluoroethane (CFC 134a or HFC-134) has been used as an alternative CFC for the regulation of specific CFCs.
(referred to as a) was noticed and it was attempted to use it as a foaming agent for a thermoplastic resin.

However, when foaming the thermoplastic resin,
When this 1,1,1,2-tetrafluoroethane is used alone as the foaming agent, the solubility of the foaming agent in the resin is relatively low as compared with the conventionally used fluorine-containing low-boiling organic compound, It was difficult to obtain a foam with high magnification (about 10 times or more).

[0007]

Therefore, the inventor of the present invention uses water as the foaming agent together with the 1,1,1,2-tetrafluoroethane to obtain the above-mentioned Japanese Patent Publication No. 52-205.
Using the technology disclosed in Japanese Patent Publication No. 00, an attempt was made to extrude and foam a thermoplastic resin such as a polyolefin resin at a high magnification (about 10 times or more).

However, since water has a poor compatibility with the resin, it is not uniformly dispersed in the molten resin in a microscopic state, and there is a problem that coarse bubbles are locally generated in the obtained foam. Further, the extrusion pressure gradually increased, and it was difficult to stably extrude and foam the resin.

An object of the present invention is to provide a foamable resin composition which has extremely small ozone layer depletion, has a high magnification, has uniform and fine closed cells, and can stably obtain a foam without discoloration or odor. To do.

[0010]

The thermoplastic resin used in the present invention includes polyethylene, polypropylene, polybutene, chlorinated polyethylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer. Polyolefin resins such as polymers and ethylene-ethyl acrylate copolymers are preferable, and further, polystyrene, polyvinyl chloride, polyvinyl fluoride, polycarbonate, polyacetal, polyphenylene sulfide, nylon 6, nylon 66, nylon 12 and the like. Polyamide resin, polyester such as polyethylene terephthalate and polybutylene terephthalate, acrylic resin, acrylonitrile-butadiene-styrene resin, fiber plastic and the like can also be used.

As the water-absorbing substance, generally, a substance which absorbs 5 times or more of its own weight of water and can release this water by heating is used. Examples of such materials are water-absorbing polymers and inorganic porous powders.

Specific examples of the water-absorbent polymer include polyacrylic acid salt-based polymers, starch-acrylic acid graft copolymers, vinyl alcohol-acrylic acid salt copolymers, polyvinyl alcohol-based polymers, polyethylene oxide-based copolymers. Etc. In particular, polyethylene oxide-based copolymers are preferable because they have excellent compatibility with various thermoplastic resins including olefin-based resins.

Specific examples of the inorganic porous powder include zeolite, activated carbon, alumina, silica gel, porous glass, activated clay, diatomaceous earth, clay and the like.

These water-absorbing substances may be melted by heating and kneaded with the resin, or may be dispersed in the resin in particles without being melted by heating. Examples of the latter water-absorbing substance include cross-linked products of water-absorbing polymers such as cross-linked polyethylene oxide and inorganic porous powder.

When the latter water-absorbing substance is used, the particle size is preferably in the range of 1 to 200 μm, and the particle size is 5
It is more preferably about 80 μm. If the particle size is too small, secondary agglomeration is likely to occur and uniform bubbles cannot be generated. On the contrary, if the particle size is too large, the bubbles become coarse or break. When the particle size is about 80 μm or less, the particles also act as a cell nucleating agent, and a foam having more uniform and fine cells can be obtained.

All of these water-absorbing substances are mixed in the range of 0.1 to 10 parts by weight, particularly 0.3 to 3 parts by weight, based on 100 parts by weight of the thermoplastic resin. Is preferred. If the amount of the water-absorbing substance is too small, water cannot be uniformly dispersed in the resin, and coarse bubbles are generated in the foam. On the other hand, if the amount of the water-absorbing substance is too large, a uniform foam cannot be obtained, and foam breakage easily occurs.

Water is mixed in the range of 0.1 to 2 parts by weight with respect to 100 parts by weight of the thermoplastic resin.
It is preferable to mix in the range of 1.5 parts by weight. If the amount of water is too small, the latent heat of vaporization for fixing the bubbles during foaming cannot be taken, and it becomes difficult to control the temperature to the foaming proper temperature. On the other hand, if the amount of water is too large, it takes time to recover the shrinkage after foaming, which causes inconvenience in production.

1,1,1,2-Tetrafluoroethane is mixed in the range of 0.1 to 10 parts by weight, and particularly 3 to 7 parts by weight with respect to 100 parts by weight of the thermoplastic resin. Is preferred. If the amount of this tetrafluoroethane is too small, the shrinkage after foaming will be remarkably slow and the recovery of the shrinkage will take time, resulting in inconvenience in production. On the other hand, if the amount of tetrafluoroethane is too large, the tetrafluoroethane will not be finely dispersed in the resin uniformly, resulting in localized coarse bubbles in the foam.

In the present invention 2, alcohol is used instead of water. As the alcohol, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, isopropanol, 2-butanol, t-butyl alcohol or the like is used. When the thermoplastic resin is crystalline, an alcohol having a boiling point below the melting point of the resin is used, and when the thermoplastic resin is amorphous, an alcohol having a boiling point below the melting point below the glass transition of the resin is used.

These alcohols have good compatibility with the resin as compared with water and thus have good dispersibility, and are uniformly dispersed in the molten resin in a microscopic state. It is not necessary to use an alcohol absorbing substance corresponding to the water absorbing substance used.

However, using an alcoholic substance,
The dispersibility of alcohol in the resin can be further improved. Here, the alcohol-absorptive substance generally means a substance capable of absorbing 5 times or more of its own weight of alcohol and releasing the alcohol by heating.

As the alcohol-absorbing substance, the same substance as the water-absorbing substance used when water is used is used. And these alcohol-absorbing substances are
It is mixed in an amount of 30 parts by weight or less with respect to 100 parts by weight of the thermoplastic resin. If the amount of the alcohol-absorbing substance is too large, a uniform foamed product cannot be obtained, and foam breakage easily occurs.

The alcohol is mixed in the range of 0.1 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin.
It is preferable to mix in the range of 3 to 3 parts by weight. If the amount of alcohol is too small, the latent heat of vaporization for fixing the bubbles at the time of foaming cannot be taken, and it becomes difficult to control the temperature to the foaming suitable temperature. On the other hand, when the amount of alcohol is too large, it takes time to recover the shrinkage after foaming, which causes not only inconvenience in production but also risk of explosion.

Thus, the foamable resin composition of the present invention is constituted. The foamable resin composition may be mixed with known additives such as a foam nucleating agent, a filler, an antioxidant, a pigment, a flame retardant, an antistatic agent and other synthetic rubbers, if necessary. Good.

To produce a foam using the expandable resin composition of the present invention, an extrusion foaming method using an extruder and a batch foaming method using a pressure vessel are mainly adopted.

In the extrusion foaming method, the following three methods are mainly adopted. The first method is to use a vent type screw extruder provided with two inlets in the vent section,
A mixture of a thermoplastic resin and a water-absorbing substance is supplied to a raw material supply port of an extruder, and a predetermined amount of water and 1,1,1 are introduced into a melt-kneaded resin from two inlets of a vent of the extruder. , 2-
This is a method in which tetrafluoroethane is injected and each of them is extruded from an extrusion die to foam a resin.

It should be noted that a predetermined amount of water may be absorbed in advance by the water-absorbing substance without injecting water from the inlet of the vent portion. Further, the mixture of the thermoplastic resin and the water-absorbing substance,
You may melt-knead and pelletize this.

In the second method, the thermoplastic resin is supplied to the raw material supply port of the extruder, and a predetermined amount of water is absorbed into the melt-kneaded resin from the two injection ports of the vent section of the extruder. This is a method in which a water-absorbing substance and 1,1,1,2-tetrafluoroethane are respectively injected and this is extruded from an extrusion die to foam a resin.

In the third method, a resin composition comprising a thermoplastic resin and a water-absorbing substance is added to a predetermined amount of water and 1,1,1.
1,2-Tetrafluoroethane is impregnated to prepare a foamable resin composition, and the foamable resin composition is supplied to a raw material supply port of an extruder and melt-kneaded. It is a method of extruding to foam a resin.

The temperature of the resin composition extruded from the mold is preferably adjusted within the range of the melting point of the resin to the melting point + 20 ° C. If the temperature of the resin composition is too low, the viscosity of the resin composition is too high, which makes extrusion difficult. Conversely, if the temperature of the resin composition is too high, the viscosity of the resin composition becomes low and the bubbles burst. It becomes easy and it becomes difficult to foam at a high magnification.

In the batch foaming method, the following method is mainly adopted. That is, a mixture of a thermoplastic resin and a water-absorbing substance, or a mixture thereof is melt-kneaded to prepare a pellet-shaped or sheet-shaped resin composition, and the resin composition, water and 1,1,1,2-tetrahydrofuran. Fluoroethane is placed in a pressure vessel such as an autoclave, and this is heated and pressurized and then depressurized to foam the resin. In order to obtain a foam having a high expansion ratio, it is preferable to heat and pressurize in the range of the melting point of the resin to the melting point + 20 ° C. and open to atmospheric pressure.

As the extrusion foaming method and the batch foaming method, the same method as described above is adopted in the second aspect of the invention. However, the alcohol-absorptive substance is mixed if necessary.

[0033]

The present invention comprises 100 parts by weight of a thermoplastic resin, 0.1 to 10 parts by weight of a water absorbing substance, and 0.1 to 2 parts by weight of water.
When foaming a foamable resin composition (invention of claim 1) consisting of 0.1 to 10 parts by weight of 1,1,1,2-tetrafluoroethane, the water-absorbing substance is uniformly dispersed in the resin. The water is absorbed by the dispersed water-absorbing substance, and thereafter, the water is released from the water-absorbing substance by heating, so that the water is uniformly dispersed in the resin.

The present invention 2 comprises 100 parts by weight of a thermoplastic resin, 0.1 to 5 parts by weight of alcohol, 1,1,1,2-
When a foamable resin composition (invention of claim 2) comprising 0.1 to 10 parts by weight of tetrafluoroethane is foamed, alcohol has good dispersibility and is uniformly dispersed in the resin.

The water or alcohol thus uniformly dispersed in the resin evaporates near the outlet of the extrusion die to become a gas, and the resin is made uniform with the gas of 1,1,1,2-tetrafluoroethane. Foam. Water or alcohol has a remarkably large latent heat of vaporization as compared with 1,1,1,2-tetrafluoroethane, and when the resin foams, water or alcohol vaporizes the latent heat of vaporization to remove the latent heat of vaporization from the resin and immobilize the bubbles. It is possible to prevent the bubbles from being broken by the expansion pressure at the time of foaming, and it is possible to uniformly and finely foam at a high magnification.

When the foam is cooled after the resin has been foamed, water or alcohol vapor condenses in the bubbles to shrink the foam. On the other hand, the gas of 1,1,1,2-tetrafluoroethane has a permeability slightly lower than that of air, and slightly expands the foam. However, since the amounts of water or alcohol and 1,1,1,2-tetrafluoroethane are adjusted appropriately, the shrinkage and expansion of the foam are largely offset, and the recovery of foam shrinkage after foaming is recovered. Be accelerated.

[0037]

EXAMPLES Examples and comparative examples of the present invention are shown below. Examples 1 to 4 and Comparative Examples 1 to 5 Low density polyethylene (density 0.921 g / cm ² , melting point 1
10.5 ° C., melt index 2.0), antioxidant (Mark323: made by Adeka Argus Chemical Co., Ltd.), talc (average particle size 10 μm) (MS: made by Nippon Talc Co., Ltd.), sodium acrylate polymer (average) A particle size of 10 μm (Sumikagel NP-1010: manufactured by Sumitomo Chemical Co., Ltd.) and a zeolite (average particle size of 10 μm) (A5: manufactured by Tosoh Corporation) were prepared. In each table, these resins and various additives are shown in parts by weight.

The above resin and various additives were mixed in the proportions shown in Table 1, and the mixed resin composition was mixed with a vent type screw extruder (bore diameter) having two inlets in the vent portion. It was supplied to a raw material supply port of 65 mm, L / D = 35) and melt-kneaded in the extruder.

Then, water was injected from the first inlet of the vent part of the extruder with a plunger pump at a rate shown in Table 1, and from the second inlet with a plunger pump at a rate shown in Table 1. Inject 1,1,1,2-tetrafluoroethane (boiling point −26.3 ° C.), melt and knead the mixture at 130 ° C., and 12 kg from an extrusion die having a die with a diameter of 2 mm set to 113 ° C. A rod-shaped foamed body was produced by extruding the foamed material at an extrusion rate of / hr to foam.

Example 5 Resin and various additives were mixed in the proportions shown in Table 1, and the mixed resin composition was melt-kneaded at 120 ° C. with a mixing roll and then pressed at 120 ° C. with a heating press to obtain a thick film. 2
mm sheets were molded. Then, this sheet was put into an autoclave, water and 1,1,1,2-tetrafluoroethane were injected into the autoclave at the ratios shown in Table 1, the autoclave was heated to 120 ° C. and left for 1 hour, then The mixture was cooled to room temperature and pelletized with a pelletizer to obtain a foamable resin composition in pellet form.

The expandable resin composition in the form of pellets was supplied to a raw material supply port of a screw extruder (diameter 65 mm, L / D = 35), and melt-kneaded at 130 ° C. in the extruder to 113 ° C. A rod-shaped foam was produced by extruding and extruding at a extrusion rate of 12 kg / hr from an extrusion die having a die having a set diameter of 2 mm.

Examples 6 to 9 and Comparative Examples 6 to 10 The resins and various additives were mixed in the proportions shown in Table 2, and the mixed resin composition was melt-kneaded at 120 ° C. with a mixing roll and then heated. Press at 120 ℃ and press to thickness 2
mm sheets were molded. Then, this sheet is put into a pressure vessel (autoclave), water and 1,1,1,2-tetrafluoroethane are injected into the vessel at the ratio shown in Table 2, and the pressure vessel is heated to 108 ° C. for 1 hour. After leaving
It was opened to atmospheric pressure and depressurized to produce a sheet-shaped foam.

Examples 10 to 14 and Comparative Examples 11 to 14 Resins and various additives were mixed in the proportions shown in Table 3, and the mixed resin composition was a vent type in which two inlets were provided in the vent part. Screw extruder (caliber 65 mm, L /
D = 35) was supplied to the raw material supply port, and this was melt-kneaded in the extruder.

Then, ethanol was injected from the first inlet of the vent part of the extruder with the plunger pump at the ratio shown in Table 3, and from the second inlet with the plunger pump at the ratio shown in Table 3, 1. Inject 1,1,2-tetrafluoroethane, melt-knead this at 130 ° C., and push out 12 kg / m from an extrusion die having a die with a diameter of 2 mm set at 113 ° C.
It was extruded at an extrusion rate of hr and foamed to produce a rod-shaped foam.

Example 15 Resin and various additives were mixed in the proportions shown in Table 3, and the mixed resin composition was melt-kneaded at 120 ° C. with a mixing roll and then pressed at 120 ° C. with a heating press to obtain a thick film. 2
mm sheets were molded. Then, this sheet was placed in an autoclave, ethanol and 1,1,1,2-tetrafluoroethane were injected into the autoclave at the ratios shown in Table 3, the autoclave was heated to 120 ° C. and left for 1 hour, and then at room temperature. The mixture was cooled to a temperature and pelletized with a pelletizer to obtain a foamable resin composition in the form of pellets.

The pelletized expandable resin composition was supplied to a raw material supply port of a screw extruder (diameter 65 mm, L / D = 35), and melt-kneaded at 130 ° C. in the extruder to 113 ° C. From an extrusion die having a die with a set diameter of 2 mm, it is extruded at an extrusion rate of 12 kg / hr to foam,
A rod-shaped foam was produced.

Examples 16 to 20 and Comparative Examples 15 to 18 Resins and various compounding agents were mixed in the proportions shown in Table 4, and the mixed resin composition was melt-kneaded at 120 ° C. with a mixing roll and then heated. Press at 120 ℃ and press to thickness 2
mm sheets were molded. Then, this sheet was placed in a pressure vessel (autoclave), ethanol and 1,1,1,2-tetrafluoroethane were injected into the vessel at the ratio shown in Table 4, and the autoclave was heated to 108 ° C. and left for 1 hour. After that, the pressure was released to the atmospheric pressure and the pressure was reduced to produce a sheet-shaped foam.

Examples 1 to 20 and Comparative Examples 1 to 18 described above
In, the foaming ratio, closed cell ratio and cell shape of the foam immediately after production were measured. Further, with respect to the foams 12 hours, 24 hours, and 10 days after the production, the foaming ratio over time was measured. The results are shown in Table 1.

The expansion ratio immediately after production was calculated by measuring the specific gravity of the foam using an electronic hydrometer (ED-120: manufactured by Mirage Co.) and dividing this by the specific gravity of the resin composition. Further, the expansion ratio with time is 1 after the production.
The volume ratio was set to 00% (reference).

The closed cell ratio is calculated by measuring the closed cell volume of the foam immediately after production using an air-comparison hydrometer (type 1000: manufactured by Tokyo Science Co., Ltd.) and dividing by the apparent volume of the foam. did.

Regarding the bubble state, the surface state of the foamed body immediately after production was observed visually, and the surface state was wrinkled, and there was no problem as a product, and the product was slightly wrinkled and slightly problematic as a product. Some samples were marked with Δ, and those with wrinkles on the surface and problems as a product were marked with x.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

[Table 3]

[0055]

[Table 4]

[0056]

The composition of the foamable resin composition of the present invention is
As described above, it is possible to obtain a stable and good thermoplastic resin foam which has extremely small ozone layer destruction, has uniform and fine closed cells at high magnification, does not cause discoloration, odor or wrinkles.

Further, foams of various shapes such as films, sheets, boards, tubes, rods, etc. can be obtained, and heat insulating materials, cushioning materials,
It can be used for a wide range of applications such as soundproofing materials, float materials, and sealing materials.

Claims (2)

[Claims] 1. 100 parts by weight of a thermoplastic resin, 0.1 to 10 parts by weight of a water absorbing substance, 0.1 to 2 parts by weight of water, 1,
A foamable resin composition comprising 0.1 to 10 parts by weight of 1,1,2-tetrafluoroethane. 2. A foamable resin composition comprising 100 parts by weight of a thermoplastic resin, 0.1 to 5 parts by weight of alcohol, and 0.1 to 10 parts by weight of 1,1,1,2-tetrafluoroethane.