JPS60224519A - Manufacturing of thermoplastic resin foaming body - Google Patents

Abstract

PURPOSE:To enhance capabilities of gas barrier and heat insulation properties, to make a surface of foaming body look neat and to increase softness by mixing a thermoplastic resin composite in which a foam regulating agent is uniformly dispersed and a thermoplastic resin which does not contain a foam regulating agent and supplying them to an extruder. CONSTITUTION:After a thermoplastic resin and a foam regulating agent are mixed by a roll kneader, etc., the mixture passes through a biaxial extruder and kneaded, and then, it is formed into a pellets. During the above process, in order to well disperse the foam regulating agent, an addition of appropriate quantity of a lubricant such as fatty acid metallic salt may be recommended. The resin composite with a regulating agent manufactured as above is mixed with a thermoplastic resin without a foam regulating agent, and it is supplied to an extruder in such a manner as to make a desired composition ratio of the foam regulating agent with thermoplastic resin. Thus, without causing a secondary agglomerate of coarse product of the foam regulating body and also, without deterioration of work environment in the manufacturing process of a foaming body, foams of a foaming body can be microminiaturized resulting in production of a foaming body which has neat and soft surface with superior capabilities of gas barrier and heat insulation properties.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing thermoplastic resin foams, particularly foam sheets.

[Prior Art #I] Conventionally, cells have been made finer in order to improve the gas barrier properties and heat insulation properties of foam sheets, improve their flexibility, and make their surfaces beautiful.

For example, when a molten thermoplastic resin containing a foaming agent is extruded from an extruder through a die to a low-pressure area to foam and create a foam, the foam control agent is added to the thermoplastic resin using a ribbon blender, tumbler mixer, etc. After being mixed with the resin, the mixture is fed into an extruder to produce a foam. However, if the amount of the cell regulator is increased in an attempt to make the cells finer in this method, the dispersion during mixing of the cell regulator and the thermoplastic resin may be insufficient, or crosstalk may occur in the extruder. Due to the possible generation of large secondary aggregates of the bubble control agent, so-called lumps, ■ The bubbles formed by foaming are not formed uniformly, resulting in a decrease in properties such as gas barrier properties and heat insulation properties, and the surface is also uneven. ■When manufacturing film-like or sheet-like foam by reducing the gap between the die openings, particles may get stuck in the openings, causing the film or sheet-like foam to deteriorate. Holes may occur in the body, cracks may appear in the extrusion direction, etc. The bubble regulating effect will be reduced due to the formation of lumps, and even if the amount of the bubble regulating agent added is increased, the bubbles will still be fine. This may cause problems such as not being able to change. In addition, as the amount of foam regulator is increased, even if a blended oil such as liquid paraffin is used, the foam regulator cannot be applied to the surface of the thermoplastic resin pellet, so when moving the blended material, bubbles may be removed. The conditioning agent tends to scatter, creating a poor working environment. Furthermore, it becomes difficult to supply a constant amount of the bubble conditioning agent due to scattering of fine powder and separation of the bubble conditioning agent and pellets in the hopper.

The ease with which lumps occur varies depending on the type and particle size of the foam regulator, as well as the mixing capacity of the blender mixer and cross-talk capacity of the extruder, so problems may occur when using the above method. Although it is not possible to unambiguously determine the amount of the foam regulator that can be added to the thermoplastic resin, the amount of the foam regulator to be added is usually 1 part or less per 100 parts (parts by weight, hereinafter the same) of the thermoplastic resin, and at most. Also, only 3 parts or less can be added. Therefore, the objectives of making the cells of the thermoplastic resin foam finer, improving its gas barrier properties and heat insulation properties, beautifying the surface of the foam, and increasing its flexibility have not necessarily been achieved.

[Summary of the Invention] In view of the above-mentioned circumstances, the present inventors have completed the present invention as a result of extensive research in order to solve such inconveniences and provide a foam having uniform and fine cells.

That is, the present invention provides a method for manufacturing a foam by extruding a molten thermoplastic resin composition containing a foaming agent from an extruder to a low-pressure area and foaming the thermoplastic resin composition, in which a foaming agent is uniformly dispersed in advance. The present invention relates to a method for producing a thermoplastic resin foam, which comprises mixing a thermoplastic resin substantially free of a cell regulator and supplying the mixture to an extruder.

[Embodiments of the invention] The thermoplastic resin used in the present invention includes styrene, α-
Styrenic polymers obtained by homopolymerization or copolymerization of styrenic vinyl monomers such as methylstyrene, α,β-dimethylstyrene, or styrene substituted with methyl, ethyl, propyl, butyl, chloro, bromine, etc.: Styrenic vinyl monomer and alkyl acrylates such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc., alkyl methacrylates such as methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, etc., or 1,3-butadiene. , acrylonitrile, vinyl acetate, dimethyl maleate, diethyl maleate, etc., and a styrenic copolymer containing 50% or more (weight %, same hereinafter) of styrenic monomer. Coalescence; high pressure polyethylene, medium pressure polyethylene, low pressure polyethylene, polypropylene, polybutene-1, ethylene-propylene copolymer,
-6- Examples include ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate-1-copolymer, olefin polymers such as chlorinated polyethylene, and copolymers mainly composed of olefins. It is not limited. These polymers may be used alone or in combination of two or more.

Among the thermoplastic resins, polymers whose main constituent units are styrene vinyl monomers containing 50% or more of styrene vinyl monomers such as styrene and α-methylstyrene are particularly preferred due to their extrudability and ease of foaming. It is preferable from the point of view.

The foam regulator used in the present invention is not particularly limited, and any commonly used foam regulator may be used. Specific examples of the bubble control agent include inorganic compounds such as calcium carbonate, talc, barium sulfate, silica, titanium oxide, clay, aluminum oxide, bentonite, and diatomaceous earth, with an average particle size of 0.1 to 20 mm; Preferably 1-10j7
Those of about i1: Organic acids such as citric acid, tartaric acid, and oxalic acid; those consisting of a combination of an acid such as boric acid and a bicarbonate or carbonate such as sodium, potassium, or ammonium. These foam regulators are usually used alone, but two or more of them may be used in combination.

Among the bubble regulators, inorganic compounds such as talc, calcium carbonate, silica, and alumina are preferred because they are inexpensive and easy to handle.

In the present invention, a thermoplastic resin composition in which a cell regulator is uniformly dispersed in advance (hereinafter referred to as an adjusted engraved resin composition) and a thermoplastic resin substantially free of a cell regulator are mixed, Supplied as an extrusion.

The above-mentioned adjusted engraved resin composition is obtained by kneading about 1 to 80 parts of a cell regulator with 100 parts of a thermoplastic resin, and then forming it into pellets or beads, and there are no particular limitations on the kneading method. , any commonly used method may be used.

Even if the amount of foam regulator is less than 1 part to the thermoplastic resin,
Although there is no problem in carrying out the present invention, if the amount of the cell regulator in the adjusted engraved resin composition is small, it may be mixed with the thermoplastic resin that does not contain the cell regulator, and the desired amount of the cell regulator may be adjusted. The proportion of the adjusted engraving resin composition increases, which is economically disadvantageous. Furthermore, in the adjusted engraving resin composition, if the amount of the cell regulator exceeds 80 parts per 100 parts of the thermoplastic resin, it becomes difficult to produce pellets or beads in which the cell regulator is uniformly dispersed.

A specific example of the cross-mixing method is a method in which the thermoplastic resin and the cell regulator are mixed using roll kneading or a Banbury mixer, and then the mixture is mixed through a twin-screw extrusion machine and then pelletized. At this time, an appropriate amount of a lubricant such as a fatty acid metal salt may be added to improve the dispersion of the foam regulator.

The adjusted engraved resin composition produced in this way is mixed with a thermoplastic resin that does not substantially contain a cell regulator, and the amount of the cell regulator is adjusted to a desired amount based on the thermoplastic resin. fed to the extruder. The amount of the foam regulator is determined depending on the desired number of cells, and is usually 0.1 to 40 parts per 100 parts of the thermoplastic resin.

In the present invention, it is advantageous to use a large number of copies, preferably 3 or more copies, more preferably -94A.

6- is 5 parts or more, and such a blending amount is preferable because the advantages of the present invention can be more fully exhibited.

In the present invention, a molten thermoplastic resin composition containing a blowing agent is extruded from an extruder to a low pressure region and foamed to produce a foamed body such as a sheet having a thickness of 0.10 to 3jIl.

The blowing agents include aliphatic hydrocarbons such as propane, butane, isobutane, pentane, neopentane, isopentane, and hexane, and alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane, and halogenated hydrocarbons. Examples include certain methyl chloride, methylene chloride, dichlorofluoromethane, chlorotrifluoromethane, dichlorodifluoromethane, chlorodifluoromethane, trichlorofluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, and the like.

These blowing agents may be used alone or in combination of two or more.

There is no particular limitation on the method of incorporating the blowing agent into the molten thermoplastic resin composition, and a commonly used method may be used, for example, using a modified engraved resin composition and a thermoplastic resin substantially free of a cell regulator. After heating and melting in the extruder, a foaming agent is continuously press-injected into the extruder, or a thermoplastic resin containing a foaming agent is pre-contained with a cell regulator.
A method is employed in which a thermoplastic resin containing a blowing agent is supplied to an extruder as a thermoplastic resin substantially free of a cell regulator. Note that the amount of the blowing agent to be contained in the molten thermoplastic resin composition may be within a commonly used range.

In the present invention, a modified engraved resin composition, a thermoplastic resin substantially free of cell regulators, and a foaming agent are supplied to an extruder, but other materials may also be used in producing the foam. Additives such as stabilizers, lubricants, plasticizers, colorants, flame retardants, etc. may be used to the extent that they do not impair the purpose of the invention. The additive may be included in the thermoplastic resin at the same time as the cell regulator, by mixing the adjusted engraved resin composition and the thermoplastic resin substantially free of the cell regulator using a blender or the like. It may be added at any time, or it may be press-fitted during mixing in a blender or the like during extrusion, and there are no particular limitations on the method of addition.

A molten thermoplastic resin composition containing a foaming agent is melt-mixed in an extruder and then extruded, usually under atmospheric pressure, to foam.

The extruder used in the present invention is not particularly limited, and a commonly used extruder can be used without any modification.

Further, the dies used can be ordinary dies such as circular dies, T dies, square dies, and coat hanger dies.

In this way, a foam with fine air bubbles, a beautiful surface, flexibility, and excellent gas barrier and heat insulation properties can be obtained.

Next, the method of the present invention will be explained in more detail based on examples.

Examples 1 to 5 Talc with an average particle size of 2.5 mm, commercially available polystyrene resin with an average particle size of 2.1 mm, and magnesium stearate were mixed in a weight ratio of 20:80:0.3. After blending, use a twin-screw extruder to uniformly mix
The mixture was mixed at 0°C and formed into a pellet. The obtained pellet and the same polystyrene resin as above which does not contain talc are mixed into a first
They were blended in proportions not shown in the table and mixed using a ribbon blender.

After that, it was fed to a 40#Iφ extruder and heated to a temperature of 180 to 220℃.
5 parts per 100 parts of resin in the mixture.
of dichlorodifluoromethane was press-fitted in an extrusion-like manner and kneaded. This molten mixture is passed through a continuation pipe of 501111φ
After feeding it to the extruder and cooling it to a temperature suitable for foaming (150°C),
φ, extruded from a circular die with a gap of 0.5 am+,
A polystyrene foam sheet was produced by stretching while foaming. The discharge amount at this time was 12 Ky/h.

The density of the obtained polypropylene sheets is 0.1 to 0.15.
Q/cyx” and the thickness and thickness 1 shown in Table 1
No coarse secondary aggregates of talc were formed in any case.

Examples 6 to 10 Bullets were produced in the same manner as in Example 1, except that the amounts of talc, polystyrene resin, and magnesium stearate used were changed to 10:90:0.3. The obtained pellet and the same polystyrene resin as used in Example 1 were blended in the proportions shown in Table 1, and a foamed sheet was produced in the same manner as in Example 1. The discharge amount at this time is 12K
It was y/h.

The resulting foam sheets all have a density of 0.1 to 0.1a.
g/, 3, and the thickness shown in Table 1 and the thickness 1 am
The number of cells was about the same, and coarse secondary aggregates of talc did not occur in any case.

Comparative Examples 1 to 8 100 parts of the same polystyrene resin as used in Example 1, which does not contain talc, was mixed with 0.1 part of liquid paraffin as a blend oil, and then 0.1 part of magnesium stearate and the mixture shown in Table 1 were mixed. 14- Talc with an average particle size of 2.5 liters as shown was blended and mixed using a ribbon blender. Thereafter, a foamed sheet was produced in the same manner as in Example 1.

The resulting foam sheets all have a density of 0.1 to 0.15.
0/cm3, and the thickness shown in Table 1 and the thickness of 1 m
However, when the amount of talc added was 0.5 parts or more, coarse secondary aggregates of talc, so-called lumps, were generated, and when the amount was more than 1 part, holes formed in the sheet. Furthermore, when the amount exceeded 3 parts, the secondary aggregates clogged the lip of the die, blocking the e1m flow path, and only a sheet with cracks in the extrusion direction could be obtained.

15-n7 - As can be seen from Table 1, when a foam is produced by the method of the present invention, as the amount of talc to the polystyrene resin increases, the number of cells per thickness 1j11 also increases (Example 1-5 and Examples 6-10). On the other hand, when producing foam using the conventional method, even if the amount of talc increases relative to the polystyrene resin, if the amount of talc exceeds a certain amount, that is, the pile of talc exceeds 1 part per 100 parts of polystyrene resin. , the increase in the number of cells per thickness becomes almost unnoticeable. These relationships are shown in Figure 1.

[Effects of the Invention] As in the present invention, when a thermoplastic resin composition containing a foaming agent is extruded from an extruder to a low-pressure region and foamed to produce a foam, the foam regulator is uniformly dispersed in advance. After producing a thermoplastic resin composition, by mixing it with a thermoplastic resin that does not substantially contain a cell regulator and supplying the mixture to an extruder, the composition can be produced without producing coarse secondary aggregates of the cell regulator. In addition, in the foam manufacturing process, the foam cells can be made finer without making the work environment worse, and the foam has a beautiful and flexible surface, and has excellent gas barrier and heat insulation properties. A remarkable effect can be obtained.

[Brief explanation of drawings]

Figure 1 shows the number of cells per line of thickness of the foam sheets obtained in Examples 1 to 10 and Comparative Examples 1 to 8 and the amount of talc per 100 parts of polystyrene resin used to produce the foam sheets. It is a graph showing the relationship between 18-

Claims (1)

[Claims] 1. A method of manufacturing a foam by extruding a molten thermoplastic resin composition containing a foaming agent from an extruder to a low-pressure region and foaming the thermoplastic resin composition in which a foaming agent is uniformly dispersed in advance. 1. A method for producing a thermoplastic resin foam, which comprises mixing a resin composition and a thermoplastic resin substantially free of a cell regulator and supplying the mixture to an extruder. 2. The method according to claim 1, wherein the thermoplastic resin is a polymer having a styrene monomer as a main constituent unit. 3 The styrenic vinyl monomer is styrene or α
-Methylstyrene.The manufacturing method according to claim 2. 4. The manufacturing method according to claim 1, wherein the bubble regulator is an inorganic compound. 5. The manufacturing method according to claim 4, wherein the inorganic compound is talc, calcium carbonate, silica, or alumina. 6. The manufacturing method according to claim 1, wherein the thermoplastic resin foam is a foam sheet having a thickness of 0.10 to 3 mm.