JPH08183870A - Production of crosslinked vinyl chloride resin foam - Google Patents

Abstract

PURPOSE: To produce a crosslinked vinyl chloride resin foam within a short time at good production efficiency. CONSTITUTION: This foam is produced by expanding an expandable composition comprising a vinyl chloride resin, an acid anhydride, an isocyanate, a blowing agent, and a tin-group metal catalyst and/or a fatty acid ester under heat and pressure and performing the crosslinking and secondary expansion of the vinyl chloride resin by bringing the obtained primary foam into contact with hot water or high-temperature steam.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a crosslinked vinyl chloride resin foam. More specifically, it relates to a method for producing a crosslinked vinyl chloride resin foam that can be suitably used as a lightweight structural material for FRP ships, a core material for FRP tanks and the like.

[0002]

2. Description of the Related Art Crosslinked vinyl chloride resin foams are excellent in compressive strength, tensile strength, bending strength, solvent resistance and the like and are light in weight. Therefore, unsaturated polyester resin foams containing a large amount of styrene monomer are used. It is used as a core material for FRP laminates using resins and as a core material for various laminated plates.

As a method for producing the crosslinked vinyl chloride resin foam, for example, a foam containing a vinyl chloride resin, a nucleating agent, an isocyanate, a dibasic acid anhydride such as phthalic anhydride or maleic anhydride, and a foaming agent. A method is known in which a volatile composition is foamed under heat and pressure to prepare a primary foam, and then secondary foaming is carried out (JP-A-5-194779).

The crosslinked vinyl chloride resin foam obtained by the above method is excellent in mechanical strength and solvent resistance, and when an adhesive is applied, the adhesive hardly impregnates it. It can be suitably used as the core material.

However, according to the above method, when a crosslinked vinyl chloride resin foam is produced, it takes a long time for the crosslinking reaction to occur, so that the crosslinked vinyl chloride resin foam can be produced more efficiently in a shorter time. There is a long-felt need for the development of a method capable of producing

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above prior art, and an object of the present invention is to provide a method for producing a crosslinked vinyl chloride resin foam which can be produced with high production efficiency in a short time. And

[0007]

The present invention was obtained by foaming a foamable composition containing a vinyl chloride resin, an acid anhydride, an isocyanate, a tin metal catalyst and a foaming agent under heat and pressure. Method for producing a crosslinked vinyl chloride resin foam, characterized in that the secondary foam is brought into contact with hot water or high-temperature steam to cross-link the vinyl chloride resin for secondary foaming (hereinafter referred to as the first invention). , And a foamable composition containing a vinyl chloride resin, an acid anhydride, an isocyanate, a fatty acid ester and a foaming agent are foamed under heat and pressure, and the obtained primary foam is brought into contact with hot water or high temperature steam. The present invention relates to a method for producing a crosslinked vinyl chloride resin foam (hereinafter referred to as a second invention), which comprises secondary foaming while crosslinking the vinyl chloride resin.

[0008]

According to the production method of the first invention, a foamable composition containing a vinyl chloride resin, an acid anhydride, an isocyanate, a tin metal catalyst and a foaming agent is foamed under heat and pressure. A crosslinked vinyl chloride resin foam is obtained by bringing the obtained primary foam into contact with hot water or high temperature steam to carry out secondary foaming while crosslinking the vinyl chloride resin.

According to the production method of the second invention, a foamable composition containing a vinyl chloride resin, an acid anhydride, an isocyanate, a fatty acid ester and a foaming agent is foamed under heat and pressure to obtain 1 A crosslinked vinyl chloride resin foam can be obtained by bringing the secondary foam into contact with hot water or high-temperature steam to cause secondary foaming while crosslinking the vinyl chloride resin.

The first aspect of the present invention is characterized in that the foamable composition contains a tin-based metal catalyst. When the tin-based metal catalyst is contained in this manner, secondary foaming is required. The time can be significantly shortened as compared with the case where the tin-based metal catalyst is not contained.

Typical examples of the tin-based metal catalyst include dimethyltin bisoctyl thioglycolate and dibutyltin diacetate, which may be used alone or in admixture of two or more.

The tin metal catalyst is blended in an amount of 0.01 parts by weight or more, preferably 0.03 parts by weight, based on 100 parts by weight of the vinyl chloride resin in order to sufficiently shorten the time required for secondary foaming. It is desirable that the amount is at least 0.3 part by weight, and in order to prevent the cell membrane from being broken due to an excessively high foaming rate, 0.3 part by weight or less, preferably 0.25 part by weight, relative to 100 parts by weight of the vinyl chloride resin. The following is desirable.

The second aspect of the present invention is characterized in that the foamable composition contains a fatty acid ester. When the fatty acid ester is contained in this manner, the time required for secondary foaming is increased. In comparison with the case where the fatty acid ester is not contained, it can be shortened significantly.

Typical examples of the fatty acid ester include fatty acid methyl ester such as methyl laurate, methyl oleate, methyl stearate and methyl caprate; fatty acid butyl ester such as butyl ricinoleate, and the like. Or a mixture of two or more kinds.

In order to sufficiently shorten the time required for secondary foaming, the amount of the fatty acid ester is 0.5 parts by weight or more, preferably 1 part by weight or more, relative to 100 parts by weight of the vinyl chloride resin. It is desirable that the amount be 20 parts by weight or less, preferably 15 parts by weight or less with respect to 100 parts by weight of the vinyl chloride resin in order to prevent the cell membrane from being broken due to an excessively high foaming rate.

In the second invention, the tin metal catalyst and the fatty acid ester may be used in combination.

The vinyl chloride resins used in the first and second inventions are compatible with vinyl chloride, including vinyl chloride homopolymers and copolymers such as vinyl chloride-vinyl acetate copolymers. It is a concept including a blended resin, for example, a mixture with at least one kind of chlorinated vinyl chloride resin, chlorinated polyethylene, ethylene-vinyl acetate copolymer and the like. The degree of polymerization of the vinyl chloride resin is usually 1000 to 4000, preferably 1500 to 3000. Further, in the present invention, among the vinyl chloride-based resins, the paste vinyl chloride-based resin can be a so-called sol-like foamable composition having fluidity, and is industrially convenient to handle. Therefore, it can be preferably used.
Here, the paste vinyl chloride resin is an almost pearl-like fine powder having a particle diameter of several μm or less, which is produced by a so-called emulsion polymerization method or micro suspension polymerization method,
The fine powder is composed of a large number of fine particles each having a smaller diameter.

The amount of the vinyl chloride resin used in the first and second inventions is usually 20 to 90% by weight, preferably 30 to 60% by weight, based on the foamable composition. If the blending amount of the vinyl chloride resin is less than the above range, the cell membrane of the foam may be broken during foaming and a good foam may not be obtained, and if it is more than the above range. However, the density of the foam tends to increase and the value as a lightweight structural material tends to be lost.

Further, since the foam object of the present invention is a crosslinked foam, an isocyanate and an acid anhydride are blended in the foamable composition.

Examples of the isocyanate used in the first and second inventions include toluene diisocyanate (TDI) and diphenylmethane diisocyanate (M
DI) and the like, and these isocyanates are usually used alone or in admixture of two or more.

The compounding amount of the isocyanate used in the first invention and the second invention is usually 10 with respect to the foamable composition.
It is preferably ˜50 wt%, especially 20-40 wt%. If the amount is less than the above range, the crosslinking effect tends to be low, and if the amount is more than the above range, the crosslinking reaction tends to take a long time. The isocyanate reacts by allowing acid anhydride and water to coexist, and carbon dioxide is generated at the same time as crosslinking proceeds. Therefore, the carbon dioxide can be used as a foaming agent. When the carbon dioxide gas thus generated is used as a foaming agent, the amount of the isocyanate compounded is 20% by weight or more based on the foamable composition,
Above all, it is desirable to set it to 25% by weight or more.

Examples of the acid anhydrides used in the first and second inventions include dibasic carboxylic acid anhydrides such as phthalic anhydride and maleic anhydride, as well as propionic anhydride, isobutyric anhydride and benzoic anhydride. And monobasic carboxylic acid anhydrides, and these acid anhydrides may be used alone or in admixture of two or more. Among these, for example, substituting a part of the dibasic acid anhydride with a monobasic acid anhydride is disclosed in the specification previously filed by the present inventors (Japanese Patent Application No. 6-290054). Is a preferred embodiment. Since the acid anhydride does not directly react with isocyanate, the foamable composition is foamed to prepare a primary foam, and the obtained primary foam is brought into contact with hot water or steam to obtain the acid anhydride. It is preferable that carboxylic acid is used as a carboxylic acid, and this is reacted with an isocyanate to cause secondary foaming and at the same time a crosslinking reaction proceeds.

The amount of the acid anhydride used in the first and second inventions is usually 0.5 to 1 of the carboxyl groups produced when the acid anhydride is reacted with water based on 1 equivalent of the isocyanate group of the isocyanate. It is desirable to adjust to 1.5 equivalents, particularly preferably 1 equivalent. When the blending amount exceeds the above range or when the blending amount is less than the above range, unreacted substances tend to remain, resulting in deterioration of various physical properties of the obtained foam.

The above-mentioned isocyanate and dicarboxylic acid react with each other to cause cross-linking to form a three-dimensional network structure. The three-dimensional network structure is entangled with the vinyl chloride resin in the order of molecular size, and a part of the resin is grafted with the vinyl chloride resin, whereby the hardness of the foam is improved and the mechanical strength is improved.

A foaming agent is blended with the foamable composition used in the first and second inventions. Such a foaming agent is
The decomposing type foaming agent is roughly classified into a decomposing type foaming agent and an evaporating type foaming agent, and any foaming agent can be used in the present invention. However, considering the foaming efficiency, the decomposing type foaming agent is preferable in the present invention.

Representative examples of the decomposition type foaming agents that can be used in the first and second inventions are, for example, azobisisobutyronitrile, azodicarbonamide, diazoaminobenzene, N, N'-dinitrosopentamethylene. Examples thereof include tetramine and p-toluenesulfonyl hydrazide. These foaming agents may be used alone or in combination of two or more.

Typical examples of evaporative foaming agents that can be used in the first and second inventions include propane, butane, and soft freons such as Freon-123. These blowing agents are used alone. Or a mixture of two or more kinds. Among these, it is preferable to use propane, butane, etc., which have a small effect on the ozone layer.

The blending amount of the foaming agent used in the first invention and the second invention differs depending on the blending amount of the isocyanate and the acid anhydride, the desired expansion ratio and the kind of the foaming agent, and therefore cannot be determined unconditionally. However, it is usually 0.1 to 10% by weight, preferably 0.2 to 7% based on the foamable composition.
% By weight. If the blending amount of the foaming agent exceeds the above range, the foamable composition tends to leak from the mold during multi-stage pressing, and if it is less than the above range, the desired foaming ratio is It tends to be hard to get.

If necessary, for example, a stabilizer, an inorganic filler (filler), a pigment, a nucleating agent and the like can be added to the foamable composition used in the first and second inventions in an appropriate amount. .

The stabilizer used in the first invention and the second invention is not particularly limited as long as it has the ability to prevent decomposition and deterioration of the vinyl chloride resin. Specific examples of such stabilizers include dibasic lead stearate, dibasic lead phosphite, tribasic lead sulfate and zinc stearate, calcium stearate, lead phosphite, and the like. The agents are used alone or in combination of two or more.

The inorganic fillers used in the first and second inventions include fibrous substances and granular substances. Typical examples of the fibrous material include rock wool, glass fiber, and ceramic fiber. Typical examples of the above-mentioned granular material include talc, calcium carbonate, shirasu balloon and the like.

The pigments used in the first invention and the second invention are for coloring the obtained foam into a desired color, and can also serve as an inorganic filler such as calcium carbonate. In addition to the white pigments that can be produced, examples include titanium white, benzidine orange, benzidine yellow, and watching red.

Examples of the nucleating agent used in the first and second inventions include talc, baking soda, citric acid, ultramarine blue,
Examples thereof include ethylene bis-stearyl amide and hydrazodicarbon amide, which may be used alone or in admixture of two or more.

In the first and second inventions, a foaming composition may be one which is usually used as an additive for plastics such as various antioxidants and antistatic agents such as ultraviolet absorbers. It can be blended.

In the first and second inventions, the foamable composition is sufficiently kneaded with a kneader such as a double-arm kneader before being filled in the mold to obtain a sol having a uniform composition. It is preferable to keep it as a thing. The temperature at the time of kneading is not particularly limited, and it is usually room temperature.

Next, the prepared foamable composition is filled in a mold made of, for example, an aluminum alloy, and the mold is set in, for example, a hydraulically driven multi-stage hot press machine, and the foamability is increased under pressure. The composition is heated.

The pressurizing and heating conditions will differ depending on the constituents of the foamable composition, but will be appropriate temperatures depending on the foamable composition, such as 150 to 200 ° C. and pressure of 100 to.
300 kg / cm ² · G is selected. When the temperature reaches the above range, it is preferable to maintain that state for about 10 to 60 minutes. After that, the pressure and heating plate temperature of the press machine is lowered to room temperature by using a cooling medium such as water while the mold is still pressurized, and the mold is opened to obtain a primary foam. .

The acid anhydride in the foamable composition does not directly react with the isocyanate, but the acid anhydride becomes a carboxylic acid in the presence of water, and the generated carboxylic acid reacts with the isocyanate. Therefore, the obtained primary foam is brought into contact with steam or hot water to allow the crosslinking reaction to proceed, and at the same time, secondary foaming is performed by the generated carbon dioxide gas. In this case, the temperature of steam or hot water is about 60 to 130 ° C., preferably 75 to 110 ° C., more preferably 90 ° C., in order to allow the crosslinking reaction and secondary foaming to proceed sufficiently.
~ 100 ° C. If the temperature is lower than 60 ° C, it does not foam to a predetermined size, or even if the foaming occurs, it takes a long time for secondary foaming, and if it exceeds 130 ° C, the cell membrane breaks. Tend. The temperature is preferably 100 ° C. or lower in order to prevent an increase in equipment cost.

The foam thus obtained has a high hardness,
Not only is it excellent in various mechanical properties, but because it has a fine cell structure, it is required to be lightweight.
It can be suitably used as a core material for RP ships and the like.

Next, the method for producing the crosslinked vinyl chloride resin foam of the present invention will be described in detail based on examples, but the present invention is not limited to these examples.

Examples 1 to 5 and Comparative Example 1 The raw materials were adjusted so that the compositions shown in Table 1 were obtained, and the total amount was 1 k.
After weighing so as to be g, the mixture was kneaded for 20 minutes at room temperature with a twin-arm kneader having an effective volume of 1 liter to obtain a foamable composition.

The foamable composition thus obtained has an inner size of 155 mm.
It was filled in an aluminum alloy mold of × 155 mm × 20 mm and set in a press machine. Pass steam through the hot press plate, raise the mold temperature to 175 ° C, and press the pressure to 210k.
After holding at g / cm ² · G for 15 minutes, industrial water is passed through the press hot plate to cool it to below 30 ° C, the clamping pressure of the press is released, and the mold is opened to open the primary foam. I got it. The size of the obtained primary foam is 180 mm x 180 m
It was m × 23 mm. After that, the obtained primary foam was secondary foamed while being crosslinked in hot water at 95 ° C., and the time until the size became 360 mm × 360 mm × 46 mm was examined. Table 1 shows the results.

The abbreviations in the table mean the following.

PSH-650A: Paste vinyl chloride resin (Kanefuchi Chemical Industry Co., Ltd., average degree of polymerization: 2400) TDI: Toluene diisocyanate PA: Phthalic anhydride ACA: Azodicarbonamide SL: Dibasic lead stearate SN : Dimethyltin bisoctyl thioglycolate CM: Methyl caprylate

[0045]

[Table 1]

From the results shown in Table 1, it can be seen that the method of Examples 1 to 5 can significantly reduce the time required for secondary foaming, as compared with the method of Comparative Example 1.

[0047]

According to the production method of the present invention, a crosslinked vinyl chloride resin foam can be obtained with good production efficiency in a short time,
The obtained foam is a FRP ship, F
It can be suitably used as a core material for RP tanks and the like.

Claims (5)

[Claims] 1. A foamable composition containing a vinyl chloride resin, an acid anhydride, an isocyanate, a tin metal catalyst and a foaming agent is foamed under heat and pressure, and the obtained primary foam is hot water or high temperature. The method for producing a crosslinked vinyl chloride resin foam, which comprises subjecting the vinyl chloride resin to secondary foaming while crosslinking the vinyl chloride resin by contacting the steam. 2. The method for producing a crosslinked vinyl chloride resin foam according to claim 1, wherein the compounding amount of the tin metal catalyst is 0.01 to 0.3 part by weight based on 100 parts by weight of the vinyl chloride resin. 3. A foamable composition containing a vinyl chloride resin, an acid anhydride, an isocyanate, a fatty acid ester and a foaming agent is foamed under heat and pressure, and the resulting primary foam is hot water or high temperature steam. A method for producing a crosslinked vinyl chloride resin foam, which comprises subjecting the vinyl chloride resin to secondary foaming while cross-linking the vinyl chloride resin. 4. The method for producing a crosslinked vinyl chloride resin foam according to claim 3, wherein the blending amount of the fatty acid ester is 0.5 to 20 parts by weight with respect to 100 parts by weight of the vinyl chloride resin. 5. The method for producing a crosslinked vinyl chloride resin foam according to claim 3, wherein the foamable composition contains a tin metal catalyst.