JPH01185338A - Production of laminated polyvinyl chloride resin foam - Google Patents

Abstract

PURPOSE:To obtain the title foam which is excellent in flatness and moldability and can give a molding of excellent dimensional stability, by foaming, by heating, a laminated sheet formed by sticking a foamable sheet comprising a PVC resin, a plasticizer, a thermally decomposable chemical blowing agent, a crosslinking agent and a heat stabilizer with a nonfoamable skinning material. CONSTITUTION:A foamable sheet of a gel fraction of 0.5-15% is obtained by irradiating a foamable sheet comprising a PVC resin (A) (e.g., PVC of a degree of polymerization of 500-2,500), a plasticizer (B) (e.g., 7-13C phthalic ester), 2-8pts.wt., per 100pts.wt. total of A+B, thermally decomposable chemical blow ing agent (C) (e.g., azodicarbonamide), 0.5-10pts.wt., per 100pts.wt. component A, crosslinking agent (D) and 0.5-5pts.wt., on the same base, heat stabilizer (E) (e.g., Zn, Sn, Ba/Zn or Ba/Sn stabilizer) with, for example, an ionizing radia tion. A laminated sheet formed by sticking this sheet with a nonfoamable skinning material comprising (flexible) PVC or PP, or the like and having a thickness of 0.2-2.0mm is heated to foam it mainly in the direction of its thickness to a density of 0.08-0.5g/cm<3>.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a composite polyvinyl chloride resin foam in which a skin material and a polyvinyl chloride resin foam are bonded together.

[Conventional technology]

Synthetic resin foams made of polyolefin, polyvinyl chloride, and polyurethane are used in a variety of fields because of their excellent heat insulation properties and soft texture.

These foams may be used alone, but a skin material is attached to the surface of the foam and the surface is decorated to create interior materials for buildings, instrument panels for interior materials for vehicles such as automobiles, etc. It is also used for door linings, ceilings, etc. These vehicle interior materials are rarely used in the form of a flat plate, and most are used after being molded. As mentioned above, composite resin foam materials obtained by laminating a skin material and a foam generally have a composite material of a polyvinyl chloride resin sheet and a polyolefin resin foam as the skin material, and a polyvinyl chloride resin sheet Composite materials with polyvinyl chloride resin foams have recently come into use.

[Problem to be solved by the invention]

Composite polyvinyl chloride resin foams are usually manufactured by bonding a foamed sheet-like material and a skin material, and therefore have the following defects during molding.

In other words, because there is a difference in shrinkage rate and shrinkage stress with respect to temperature between the skin material and the foam sheet, there is a disadvantage that the product dimensions differ at the time of molding and after cooling by heat radiation. If the conditions are not selected in consideration of the dimensional difference, a product with the desired dimensions cannot be obtained.

The purpose of the present invention is to improve the above-mentioned deficiencies of the prior art and to provide a new method for manufacturing a composite polyvinyl chloride resin foam, which allows a product with constant product quality and excellent dimensional stability to be obtained by a simple method. This is what I am trying to do.

[Means to solve the problem]

In order to achieve the above object, the present invention consists of the following configuration. That is, it consists of a polyvinyl chloride resin, a plasticizer, a pyrolytic chemical foaming agent, a crosslinking aid, and a heat stabilizer, and the content of the pyrolytic chemical foaming agent is 100% by weight of the total weight of the polyvinyl chloride resin and plasticizer. 2 to 8 parts by weight, and the gel fraction is 0.5 to 15%.Heating the composite sheet 1~ in which a foamable sheet and a non-foamable skin material are laminated, mainly in the thickness direction. This is a method for producing a composite polyvinyl chloride resin foam, which is characterized by foaming at a high temperature.

The present invention will be explained in more detail.

The polyvinyl chloride resin used in the present invention has a degree of polymerization of 50
0 to 2,500 polyvinyl chloride, or a copolymer or graft copolymer in which the vinyl chloride moiety has a degree of polymerization of 500 to 2,000 (for example, a copolymer with ethylene, vinyl acetate, acrylic acid, or acrylic ester), etc. Suitably used.

Plasticizers used in the present invention include plasticizers made of phthalate esters having 7 to 13 carbon atoms (for example, dioctyl phthalate), polyester-based or polyurethane-based plasticizers,
Examples include polymeric plasticizers such as ethylene-vinyl acetate-carbon oxide and aliphatic polyester polymers.

The thermally decomposable chemical blowing agent used in the present invention is not particularly limited, and examples include azodicarbonamide, 4,4'-
Known materials such as oxybisbenzosulfonyl hydrazide and dinitrosopentamethylenetetramine can be used, and the content thereof is 2 to 8 parts by weight based on a total of 100 parts by weight of the polyvinyl chloride resin and plasticizer. If the amount is less than 2 parts by weight, sufficient foaming cannot be obtained, while if it exceeds 8 parts by weight, foaming mainly in the thickness direction becomes difficult. In addition, in order to adjust the decomposition temperature, a decomposition accelerator such as zinc oxide or zinc stearate may be added.

The crosslinking aid used in the present invention includes divinylbenzene,
Polyfunctional monomers, dimers, and trimers having two or more vinyl double bonds, such as diallyl phthalate and trimethylolpropane triacrylate, can be used. The content thereof is preferably 0.5 to 10 parts by weight per 100 parts by weight of the polyvinyl chloride resin.

The heat stabilizer used in the present invention may be any commonly used vinyl chloride resin and may include metal soaps, epoxidized soybean oil, mercapto, etc., but preferably zinc, tin, barium/zinc, or barium. /Tin-based stabilizers are preferable. The content thereof is preferably 0.5 to 5 parts by weight per 100 parts by weight of the polyvinyl chloride resin.

The foamable sheet used in the present invention is composed of a polyvinyl chloride resin, a plasticizer, a thermally decomposable chemical foaming agent, a crosslinking aid, and a heat stabilizer, but the foamable sheet used in the present invention may not impair the objective effects of the present invention. Other resins, crosslinking agents, other fillers, coloring agents such as @li, etc. may be appropriately blended within the range.

Other resins include polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid-acrylic acid alkyl ester ternary copolymer, ethylene-acrylic acid alkyl ester-maleic anhydride. Examples include an acid ternary copolymer, and (2) a tyrene-methyl methacrylate maleic anhydride ternary coelectrolyte.

Examples of the crosslinking agent include dicumyl peroxide and 2°6-ditertiary-butyl peroxide.

In the present invention, the gel fraction of foamable seams 1 to 1 is 0.5.
~15%. If the gel fraction is less than 0.5%, it is undesirable because it will substantially cause "sagging" at high temperatures and deteriorate compression recovery properties, whereas if it exceeds 15%, foaming will be maintained mainly in the thickness direction. This is undesirable because it results in three-dimensional (vertical, horizontal, and thickness directions) foaming, which causes wrinkles or cracks in the skin material, and poor dimensional stability.

The method of imparting the gel fraction of the present invention includes a method of irradiating the foamable sheet 1~ with ionizing radiation, a method of adding peroxide or a peroxide and an organic silane compound to the foamable sheet 1~ in advance. There is a method of adding a photosensitizer such as anthraquinone to the foamable sheet in advance and irradiating it with ultraviolet rays, etc. Among them, a method of irradiating with ionizing radiation is preferred. The ionizing radiation may be irradiated before or after bonding the non-foaming skin material.

The non-foaming skin material used in the present invention is made of, for example, polyvinyl chloride, polypropylene, ABS, hardboard, or various fabrics, and preferably has a thickness of 0.2 to 2. Qm
Particularly suitable is a non-foaming skin material made of soft polyvinyl chloride.

In the present invention, foaming mainly occurs in the thickness direction, which is determined by the ratio of the length and width of the foamable sheet before and after foaming, and the W(
However, L=l/lo, W=w/wO1io
is the length of the foamable sheet before foaming, 1 is the length of the foamable sheet after foaming, WQ is the width of the foamable sheet before foaming, and W is the width of the foamable sheet after foaming). 0 or more 1.5
Indicates that it is less than Length ratio or width ratio before and after foaming W
When exceeds 1.5, it corresponds to three-dimensional foaming behavior, so
This is not preferable because the dimensional stability of the composite amount is extremely deteriorated and the shape of the composite amount is deteriorated. The ratio T of the thickness of the foamable sheet before and after foaming (where T = t/lo, tO is the thickness of the foamable sheet before foaming, and t is the thickness of the foamable sheet after foaming) is usually 7 or less. be. When the thickness ratio T before and after foaming exceeds 7, shrinkage in the length and width directions is reduced, which impairs the dimensional stability of the composite quantity, which is not preferable.

In the present invention, the density of foamable sheets 1 to 1 after foaming is usually 0.08 to 0.5 C]/cm<3>. 0.080/C
...If it is less than 3, waving phenomenon will occur in the foam and the flatness of the composite will deteriorate, so it is not preferable.
/cm3 is not preferable because the cushioning properties of the foam decrease.

Next, the method of the present invention will be explained in more detail. However, the present invention is not limited to the following description.

First, after blending the polyvinyl chloride resin, plasticizer, thermally decomposable chemical blowing agent, crosslinking aid, heat stabilizer, and other ingredients as necessary, use a ribbon blender, Henschel mixer, etc. Disperse and mix using vinyl processing equipment. Next, the dispersed and mixed composition is molded into a sheet using an extruder and a calender to obtain foamable sheets 1 to 1. Next, the foamed sheet is irradiated with ionizing radiation, specifically an electron beam accelerated irradiation machine, at an average absorbed dose of about 0.5 to 15 Mrad to crosslink the sheet so that the gel fraction becomes 0.5 to 15%. Apply processing.

A non-foamable skin side made of a polyvinyl chloride sheet, an ABS resin sheet, a polypropylene sheet, a hardboard, or a fabric-like material of various types is laminated to this foamable sheet to form a composite sheet 1. Means for lamination As the method, known methods such as a heat fusion method and an adhesive method can be applied.

When the above-mentioned composite sheets 1 to 1 are heated, the foamable sheet, which is one element of the composite sheet, foams. Foaming is carried out by known means, for example, by heating in a hot air oven or on a salt bath set at a temperature higher than the decomposition temperature of the blowing agent. Foaming can also be done simultaneously with thermoforming. This is because, in the present invention, foaming occurs only in the direction mainly in the thickness direction.

Since the composite polyvinyl chloride resin foam obtained by the present invention has a foamed portion mainly in the thickness direction, the amount of residual strain after forming by vacuum forming etc. is small, resulting in , good dimensional stability after molding.

〔Example〕

Next, the present invention will be explained in more detail based on Examples.

Gel fraction (%) used in the present invention, density of foam (
The characteristic values for CI/cm3) and moldability H/D are values obtained by the following measuring method.

(a) Gel fraction (%) Cut the sample into pieces and accurately weigh 0.2C]. Precisely weighed sample
After immersing it in 20°C Te1~Ralin for 2 hours to elute the dissolving power, take out the insoluble matter and wash it with acetone.
Dry for 1 hour in a vacuum drying mold at 0'C. The weight W1 (q) of this dried insoluble matter is accurately weighed, and the gel fraction (%) is determined using the following formula (the number n is 10).

Gel fraction - (Wllo, 2)
(cm), then accurately weigh the weight W2 (g),
The density (q/c+++3>) is determined using the following formula, and its reciprocal is defined as the expansion ratio (times) (the number n is 10).

Density - W2/(10X10Xt) (C) Formability H/D In the vacuum forming method, a cylindrical mold is used, and the moldability is determined by the ratio of the depth H (Cm) to the diameter D (Cm) of the mold. H/D is expressed as H/D, and moldability H/D is 140 to 160'
The foamed material heated to C is vacuum-formed, and the foamed material is stretched to maintain the shape of the mold without tearing (the number n is 3).

(d) Dimensional retention of molded product (%) This is the ratio of the dimension d of the molded product after vacuum forming in a mold and left at room temperature for 24 hours to the dimension d of the mold, and was calculated using the following formula. .

Molded product dimensional retention - d/do Xl 00 Example 1 100 parts by weight of polyvinyl chloride resin with a degree of polymerization of 1050, 40 parts by weight of dioctyl phthalate (plasticizer), 3 parts by weight of azodicarbonamide (blowing agent), trimethylolpropane A mixture containing 0.8 parts by weight of triacrylate and 0.5 parts by weight of dibutyltin laurate was uniformly mixed using a Henschel mixer to obtain a foaming composition. This composition was introduced into an extruder set at a temperature that did not decompose the blowing agent.
A foamable sheet of m was prepared. A sheet made of polyvinyl chloride resin (thickness: 0.4 mm) is bonded to this foamable sheet using a polyester adhesive, and then ionizing radiation of 6 Mrad is irradiated from the foamable sheet side to form a foamed composite sheet. And so. This composite sheet was heated to a temperature higher than the decomposition temperature of the foaming agent to foam the foamable sheet portion. The behavior of this foam during foaming expanded in the thickness direction, resulting in a composite foam with good flatness. The foam portion of this composite foam had a thickness of 1.5 mm, a density of 0.30 Q/cm3, and a gel fraction of 3.5%.

This composite foam was vacuum-formed using cup-shaped molds having a diameter D=50 mm and different depths H. This molded article had excellent moldability and at the same time had a small difference between the dimensions of the molded article after being left at room temperature for 24 hours and the dimensions of the molding die, that is, had an extremely low shrinkage rate. The results are shown in Table 1.

Example 2 The composition of the mixture was the same as in Example 1 except that 6 parts by weight of azodicarbonamide (a blowing agent) was added, and the thickness was 1. It was molded into a foamable sheet of □mm. This sheet was heated to 140° C., and a polyvinyl chloride resin sheet heated to 180° C. was bonded to the composite sheet using a so-called heat fusion method, in which air was not trapped. 8Mra for this composite sheet
A composite sheet for foaming was prepared by irradiating the electron beam d. This product was heated and foamed in the same manner as in Example 1 to obtain a composite foam.

The foam part of this composite foam had a thickness of 5.5 mm, a density of 0.130 Q/cm3, and a gel fraction of 4.5%, and the same molding results as in Example 1 were shown in Table 1. It was excellent.

Example 3 A foaming composition with a thickness of 1.5 mm was prepared from the same foaming composition as in Example 1 except that 8 parts by weight of azodicarbonamide (foaming agent) was added.
It was made into a foamable sheet. After irradiating this sheet with an electron beam of 10 Mrad, a polyvinyl chloride resin sheet was bonded to the sheet using a polyurethane adhesive to obtain a foamed composite sheet. This sheet was foamed in the same manner as in Example 1 to obtain a composite foam. This composite foam also expanded uniformly in the thickness direction and had good flatness. The thickness of the foam part of this composite foam is f3, 3mm, and the density is 0°10
Cl/cm3, gel fraction was 10%, Example 1
The molding results similar to those shown in Table 1 were excellent.

Comparative Example 1 From the same foaming composition as in Example 1 except that 13 parts by weight of azodicarbonamide (a blowing agent) and 1.5 parts by weight of 1 to 1-rimethylolpropane triacrylate were added, a foaming composition with a thickness of 1.
．． It was made into a foamable sheet of Qmm.

After irradiating these sheets 1 to 1 with an electron beam of 15 Mrad, a polyvinyl chloride resin sheet was attached using a polyester adhesive to form a foamed composite sheet.

As a result of foaming this sheet in the same manner as in Example 1, mountain wave-like undulations were generated, resulting in a composite foam with poor flatness. Formability was also reduced due to poor flatness, and shape retention was also poor.

The results are shown in Table 1.

Comparative Example 2 The mixture composition was the same as in Example 1, and the foam sheet had the same thickness as in Example 1. 20Mra for this seat
After irradiating with the electron beam d, a polyvinyl chloride resin sheet was bonded using a polyurethane adhesive to obtain a foamed composite sheet. As a result of foaming this sheet in the same manner as in Example 1, expansion in the vertical and horizontal directions was observed, small wrinkles were generated on the surface of the obtained composite foam, and the flatness was poor.

Moreover, moldability was also poor. The results are shown in Table 1.

Comparative Example 3 A composite foam was prepared in the same manner as in Example 1 except that the amount of azodicarbonamide (foaming agent) was 2 parts by weight. The resulting composite foam had poor cushioning properties. The results are shown in Table 1.

〔Effect of the invention〕

The composite polyvinyl chloride resin foam obtained by the method of the present invention has excellent flatness and moldability, and the molded product obtained by molding the composite polyvinyl chloride resin foam maintains molded dimensions. Excellent quality.

Claims (1)

[Claims] (1) Consisting of polyvinyl chloride resin, plasticizer, pyrolytic chemical blowing agent, crosslinking aid, and heat stabilizer, the content of pyrolytic chemical foaming agent is 1 in total of polyvinyl chloride resin and plasticizer.
0.00 parts by weight, and the gel fraction is 0.00 parts by weight.
Production of a composite polyvinyl chloride resin foam, which is characterized by heating a composite sheet in which a foamable sheet and a non-foamable skin material of 5 to 15% are laminated together to foam mainly in the thickness direction. Method.