JPH0230342B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for producing a polyvinyl chloride resin foam molded article, particularly a method for continuously producing a polyvinyl chloride resin foam molded article having a uniform fine cell structure and a high expansion ratio at a low cost. Conventionally, the method for manufacturing polyvinyl chloride resin foam moldings has been as follows: (1) Adding and mixing a so-called decomposable foaming agent, which becomes a gaseous substance upon decomposition, to vinyl chloride resin;
(2) Mix vinyl chloride resin and plasticizer to form a paste (plastisol) and then mechanically foam it. , or a method of adding and mixing a decomposable blowing agent to the plastisol and then heating it to gel and foam the desired product; (3) a mixture containing a decomposable blowing agent;
(4) In the mold, a vinyl chloride resin and a decomposable blowing agent (if necessary, a volatile organic foam is added). A known method is to fill the foam with a foaming agent, a swelling organic solvent, and a softening agent, pressurize and heat it to melt it into a gel, cool it, and then heat it again to foam it. However, methods (1) to (3) above cannot produce a hard or semi-hard foam, and method (4) requires a batch method, and the manufacturing process is complicated, resulting in foaming. Because it takes a lot of time to get in shape,
The final product will be expensive,
Each has their own drawbacks. The present inventors have conducted repeated research on a method for obtaining a vinyl chloride resin foam molded product without such disadvantages, and have first added a heat stabilizer to a vinyl chloride resin, a nucleating agent such as talc, and an acrylic resin. (or styrene-based resin), a decomposable blowing agent such as azodicarbonamide-based compound, etc. is supplied to an extruder, and the resin composition is heated and gelled in this extruder. We propose a method in which an organic solvent-based blowing agent such as propane, butane, pentane, methyl chloride, trichlorofluoromethane, dichlorotetrafluoroethane, or aliphatic halogenated hydrocarbon or aliphatic halogenated hydrocarbon is injected under pressure at temperatures below ℃ and extrusion foam molding is performed. (Unexamined Japanese Patent Publication No. 55-149328
No. 55-152725). However, these methods require (i) extremely high injection pressure during press-fitting, and in order to improve dispersion into the resin composition, it is necessary to apply strong mechanical shear to the resin composition; , and in order to promote the dissolution of the organic blowing agent into the resin, it is necessary to raise the temperature to lower the melt viscosity of the resin. (ii) Also, in order to improve the dispersion of the organic blowing agent into the resin composition, , it is necessary to lengthen the dispersion mixing zone; (iii) the resin temperature in the dispersion mixing zone is increased;
It is necessary to uniformly cool this to a temperature suitable for foam molding and then extrude it into foam. It has been difficult to stably produce a foam molded product having a cell structure. As a result of intensive research to solve this problem, the present inventors found that 100 parts by weight of at least one of the aliphatic hydrocarbons and aliphatic halogenated hydrocarbons mentioned above as a volatile organic blowing agent, and a vinyl chloride resin. When used in combination with 1 to 50 parts by weight of at least one compatible alcohol compound with a boiling point of 200°C or less, this mixed organic blowing agent can be easily and efficiently press-fitted into the resin composition in the extruder. Since it is dissolved and dispersed in the resin component, the above-mentioned
The present invention was completed after confirming that the problems (i) to (iv) were solved. That is, the present invention supplies a vinyl chloride resin composition to an extruder, and then adds (a) an aliphatic compound having a boiling point of 90°C or lower (preferably 70°C or lower) to the resin composition heated in the extruder. At least one selected from hydrocarbons and aliphatic halogenated hydrocarbons100
and (b) 1 to 50 parts by weight of at least one alcohol compound with a boiling point of 200° C. or lower, press-injected at a rate of 1 to 30 parts by weight per 100 parts by weight of the resin composition, The present invention relates to a method for producing a vinyl chloride resin foam molded article, which is characterized by melt-kneading and then extrusion foam molding. According to the method of the present invention, the required amount of the mixed organic blowing agent can be easily uniformly dispersed (dissolved and dispersed) in the heated resin composition in the extruder,
As a result, a polyvinyl chloride resin foam molded article having a uniform fine cell structure and a high expansion ratio can be produced continuously at low cost. The present invention will be explained in detail below. The organic blowing agent used in the method of the present invention is composed of at least one of the above-mentioned components (a) and (b), including an aliphatic hydrocarbon having a boiling point of 90°C or less and aliphatic halogenated hydrocarbons such as propane, butane, isobutane, pentane, neopentane, n-hexane, isohexane, n-heptane, methyl chloride, methylene chloride,
Chloroform, carbon tetrachloride, ethyl chloride, ethylidene chloride, trichloroethylene, 1,2-dichloroethane, trichlorofluoromethane, dichlorodifluoromethane, bromotrifluoromethane,
Examples include tetrafluoromethane, dichlorofluoromethane, chlorotrifluoromethane, trifluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, dibromotetrafluoroethane, chloropentafluoroethane, hexafluoroethane, chlorodifluoroethane, and difluoroethane. In addition, these are 2
You may use more than one species in combination. If an aliphatic hydrocarbon or aliphatic halogenated hydrocarbon with a boiling point higher than 90°C is used, the foam will shrink significantly during foam molding, and a foam with a uniform cell structure will not be obtained. It is necessary to use a component (a) with a boiling point of 90°C or lower, and it is particularly desirable to use a boiling point of 70°C or lower. On the other hand, the component (B) used together with the component (A) above must be an alcohol compound that is compatible with the vinyl chloride resin, but this compound is particularly
It has a boiling point of 200°C or lower, preferably 150°C or lower, specifically methanol, ethanol, n-
Propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-
Examples include butanol, n-amyl alcohol, sec-amyl alcohol, tert-amyl alcohol, 3-pentanol, methylamyl alcohol, 2-ethylbutanol, n-hexyl alcohol, and the like. The use of these is not limited to one type, and two or more types may be used simultaneously. The above-mentioned component (a) is mainly used for the main foaming caused by vaporization when the mixture melt-kneaded in the extruder is discharged under atmospheric pressure, the homogenization of cells formed by foaming, and the formation of foamed products due to the latent heat of vaporization. Component (B) mainly serves to lower and stabilize the injection pressure when injecting the organic blowing agent into the resin composition in the extruder, and to lower the resin melt viscosity in the extruder. The mixing ratio of component (a) and component (b) is 1 to 50 parts by weight of component (b) to 100 parts by weight of component (a). Parts by weight are preferably 5 to 30 parts by weight, and the organic blowing agent consisting of components (a) and (b) must be used in an amount of 1 to 30 parts by weight per 100 parts by weight of the vinyl chloride resin composition. In the method of the present invention, generally, a raw vinyl chloride resin composition is first prepared in advance using a mixer such as a super mixer, and this is fed to an extruder, and then the resin composition is heated in the extruder. A predetermined amount of an organic blowing agent consisting of components (a) and (b) described above is press-fitted from the middle of the cylinder, and the press-fitted organic blowing agent is uniformly mixed into the resin composition in a melt-kneading zone inside the cylinder. This is carried out by a method of dispersing (dissolving and dispersing) the resin composition, then uniformly cooling the resin composition to a temperature suitable for foaming, and extruding it into the atmosphere or into a reduced pressure section to perform foam molding. The organic blowing agent may be press-fitted at any time as long as it does not cause the organic blowing agent to back into the resin composition supply port and cause the resin composition to be bitten into the resin composition. The resin composition is often in a semi-gelled state or completely gelled, and in either of these states, the organic blowing agent is easily and uniformly dispersed in the resin composition, resulting in uniform cells. A molded article having a structure and a high expansion ratio can be obtained. The raw material vinyl chloride resin composition used in the method of the present invention is a mixture of vinyl chloride resin as a main ingredient and various necessary ingredients or additives. For example, from the standpoint of obtaining a better foam molded product, a pyrolytic foaming agent and a high melting point fine powder substance are used to adjust the cell structure uniformly and finely during foam molding to 100 parts by weight of vinyl chloride resin. 0.01 part by weight or more of a cell homogenization aid selected from 0.5 to 30 parts by weight of acrylic resin and/or styrene resin to prevent shrinkage, and if necessary, various additives conventionally added to vinyl chloride resin in amounts that do not impair the purpose or effect of the present invention. It is preferable to use stabilizers, lubricants, fillers, etc.). Vinyl chloride resins are not limited to polyvinyl chloride, but include various copolymers mainly composed of vinyl chloride,
Graft copolymers, polymer blends, etc. are included, and comonomers copolymerizable with vinyl chloride in this case include vinyl acetate, vinylidene chloride, acrylic acid and its esters, methacrylic acid and its esters, acrylonitrile,
One or more of methacrylonitrile, maleic acid and its esters or anhydrides, fumaric acid and its esters, olefins such as ethylene and propylene, and vinyl ethers, and resins used in the polymer blend include Polymers having good miscibility with vinyl chloride resins, such as polyvinylidene chloride, ethylene-vinyl acetate copolymers, ABS resins, MBS resins, chlorinated polyethylenes, and synthetic rubbers such as NBR and SBR. Acrylic resins can uniformly promote gelation of vinyl chloride resins, appropriately increase resin viscosity, provide rubber elasticity, and improve the tensile strength or elongation rate of vinyl chloride resins at high temperatures. ,
i.e. 20 as 0.1g/100ml chloroform solution
The reduced viscosity measured at °C is 3.0 dl/g or more,
It is desirable to select and use an acrylic resin with a high polymerization degree that is higher than the polymerization degree of the raw material vinyl chloride polymer used and has good compatibility. Examples of copolymers include copolymers of methyl methacrylate and acrylic ester, and copolymers of monomers copolymerizable with these. In addition, similar to the aforementioned acrylic resins, styrene resins have good compatibility with vinyl chloride resins, increasing the melt viscosity of the resin when melting the resin composition and imparting rubber elasticity. A product that can improve the tensile strength or elongation rate of the resin at high temperatures and prevent cell coalescence or shrinkage during foaming to obtain the desired highly foamed molded product, i.e., as a 0.1 g/100 ml chloroform solution. It is desirable to select and use a high degree of polymerization that has a reduced viscosity of 3.0 dl/g or more when measured at 20°C and has good compatibility with the vinyl chloride resin used. Copolymers of this and acrylonitrile and/or monomers copolymerizable with these (acrylic esters, methacrylic esters, maleic esters, fumaric esters) are preferred. Note that, if the polymerization degree of the vinyl chloride resin used as the main resin is high, it is desirable to use a styrene resin having a high polymerization degree corresponding to the high polymerization degree of the vinyl chloride resin used as the main resin. Furthermore, examples of thermally decomposable blowing agents include azodicarbonamide, azobisisobutyronitrile, diazoaminobenzene, diethyl azodicarboxylate, diisopropylazodicarboxylate,
Azo blowing agents such as diazoaminobenzene, N,
N'-dinitrosopentamethylenetetramine, N,
Nitroso blowing agents such as N'-dimethyl-N,N'-dinitrosoterephthalamide, benzenesulfonyl hydrazide, toluenesulfonyl hydrazide, 3,3'-disulfone hydrazide phenyl sulfone, toluene disulfonyl hydrazone, thiobis(benzenesulfonyl hydrazide) ), toluenesulfonyl azide, toluenesulfonyl semicarbazide, 4,4'-oxybis(benzenesulfonylhydrazide) and other sulfonyl hydrazide foaming agents, or sodium bicarbonate. In addition, high melting point fine powder substances include inorganic substances such as calcium carbonate, talc, barium sulfate, fumed silica, titanium oxide, clay, aluminum oxide, bentonite, diatomaceous earth, and citric acid, tartaric acid, oxalic acid, etc. Examples include those consisting of a combination of an organic acid or an acid such as boric acid and a bicarbonate or carbonate of sodium, potassium, or ammonium. By extrusion foam molding according to the method of the present invention described above, a polyvinyl chloride resin foam molded product with a high expansion ratio and having a uniform fine cell structure in various shapes such as plate, sheet, rod, and tube shapes is produced. can be manufactured continuously at low cost. Next, specific examples will be given. Examples (Experiment Nos. 1 to 11) 100 parts by weight of vinyl chloride resin of various polymers (as shown in the table), 2 parts by weight of lead-based stabilizer, 1 part by weight of calcium stearate, 3 parts by weight of talc, Cellmic 133 (3 parts by weight) Kyokasei, azodicarbonamide-based compound, decomposition temperature 130-180°C) 0.5 parts by weight, and acrylic polymer (copolymer consisting of 80% by weight of methyl methacrylate and 20% by weight of n-butyl acrylate, reduced viscosity) 11.5 dl/g) were mixed in a super mixer. Each resin composition thus obtained was extruded and foam-molded into a plate shape using the following two extruders connected together. However, the type and injection amount of the organic blowing agent were as shown in the table. [Extruder] The first extruder has a diameter of 50 mm and L/D = 30,
The cylinder of this extruder is equipped with a blowing agent injection hole through which an organic blowing agent can be injected using a dual plunger pump. The second extruder has a diameter of 65 mm L/D=28 and is connected to the tip of the first extruder. A die of 4 mm T x 450 mm L is attached to the tip of this second extruder. [Temperature conditions of first extruder, etc.] Cylinder temperature: 1C 90-120℃ 2C 120-180℃ 3C 150-170℃ 4C 150-170℃ Connecting pipe temperature: 150-170℃ Organic blowing agent injection pressure: In the table Description Rotation speed: 50 rotations [second extruder temperature conditions, etc.] Cylinder temperature: 1C 145-160℃ 2C 135-150℃ 3C 125-140℃ Die temperature: 120-135℃ Rotation speed: 15-18 rotations Die pressure : Listed in the table Extrusion foam molding under the above conditions (extrusion amount approx. 35-40
When the density (g/cm ³ ) and cell state of the plate-like foam obtained using the same method were examined, the results were as shown in the table. In the table, Experiments Nos. 1 to 5 are of the present invention, and Experiments Nos. 6 to 12 are comparative examples. In addition, among the organic blowing agents in the table, TCFE, CH, dipentene and
nDOL is a compound other than components (a) and (b) of the present invention. [Cell Condition Judgment Criteria] A: Consists of a fine uniform cell structure with a cell diameter of 1000 μm or less, and has an excellent appearance. B: The cell diameter is 1000 μm or more, and the cells are rough and non-uniform. [Abbreviations used in the table] TCFM: Trichloromonofluoromethane DCFM: Dichlorodifluoromethane CDFE: Chlorodifluoroethane TCE: Trichloroethylene TCM: Carbon tetrachloride MLC: Methyl chloride MNC: Methylene chloride TFM: Tetrafluoromethane iPOL: Isopropanol nPOL: n-propanol nDOL: n-decanol CH: cyclohexane TCFE: tetrachlorodifluoroethane

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Claims (1)

[Claims] 1. Supplying a vinyl chloride resin composition to an extruder,
Then, in the resin composition heated in this extruder, (a) at least one selected from aliphatic hydrocarbons and aliphatic halogenated hydrocarbons having a boiling point of 90°C or less is added.
An organic blowing agent consisting of 100 parts by weight of seeds and (b) 1 to 50 parts by weight of at least one alcohol compound having a boiling point of 200°C or less is press-ined at a ratio of 1 to 30 parts by weight per 100 parts by weight of the resin composition. A method for producing a polyvinyl chloride resin foam molded article, which comprises melt-kneading and extrusion foam molding.