JPH0511757B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is a polyolefin resin foam that is used in automobiles, etc., in which a skin material is bonded to one of both surfaces and a thermoplastic resin for aggregate is integrally molded to the other surface. Related to vehicle interior molded products. [Prior Art] The following are known as conventional vehicle interior molded products of this type. The first conventional example is the so-called injection-integral molding method,
A skin material such as a soft vinyl chloride sheet is laminated on one surface of a polyolefin resin foam using an adhesive method or an extruder to obtain a composite material. It is molded to fit the mold, set in the mold, and a thermoplastic aggregate resin such as molten polypropylene resin is injected into the remaining space in the mold on the opposite side from the skin material. Then, a vehicle interior molded product having a desired shape is obtained. Second conventional example This is the so-called vacuum compression molding method, as shown in Japanese Patent Application Laid-Open No. 54-10367, in which aggregate molded in advance into a desired shape is set in the male die of a mold. An adhesive dispersed with an organic solvent is applied to the surface of the aggregate by spraying, etc., and then a composite material made of a polyolefin resin foam laminated with a skin material heated at a high temperature is placed on the surface of the aggregate, and then the female mold and the composite material are placed. The air in the space between the mold and the composite material and the space between the composite material and the aggregate is removed by vacuum suction, and the female mold and the composite material, and the composite material and the aggregate are brought into close contact with each other, and then the skin of the composite material is removed. Compressed air is supplied from the material side to compress and pressurize the composite material toward the aggregate side, thereby obtaining a vehicle interior molded product having a desired shape. [Problems to be Solved by the Invention] However, the first and second conventional examples described above each have the following drawbacks. (i) Disadvantages of the first conventional example There is a disadvantage that productivity decreases because the composite material must be molded into the desired shape in advance, and the melting temperature of the thermoplastic resin for the aggregate to be injected is high. The polyolefin resin foam is heated to a high temperature by the high temperature resin, pressure is applied to the polyolefin resin foam in the heated state, and the aggregate thermoplastic resin side of the polyolefin resin foam becomes high temperature. As the bubbles expand and deform and are destroyed, the destruction spreads to the bubbles on the skin material side, causing unevenness on the skin material side.
The disadvantage was that it was easy to produce defective products and the product yield was low. (ii) Disadvantages of the second conventional example: In addition to having to mold the aggregate into a desired shape in advance, adhesive must be applied to the surface of the aggregate, which increases the number of steps and reduces productivity. There was a drawback that it deteriorated. Further, an organic solvent is required to disperse the adhesive, which worsens the working environment, poses a risk of fire due to its flammability, and has the disadvantages of increased cost. The present invention was made in view of these circumstances, and it improves quality and productivity by not using adhesives during integral molding and by eliminating the need for prior molding of composite materials and aggregates. The purpose of the present invention is to provide a vehicle interior molded product that can be produced with high levels of both. [Means for Solving the Problems] In order to achieve the above object, the vehicle interior molded product according to the present invention is a polyolefin resin foam with a gel fraction of 35% or more, The average foaming ratio of the thickness from the surface to 0.5mm is larger on one side than on the other.
In addition, a skin material is bonded to the side of the polyolefin resin foam with a higher average expansion ratio, and the difference in expansion ratio between the two is 2 to 20 times, while hot stamping is applied to the side of the polyolefin resin foam with a lower average expansion ratio. It is characterized in that the thermoplastic resin for aggregate is integrally molded using a molding method. In the hot stamping mold method, a molten thermoplastic resin for aggregate is distributed and supplied on one press surface of a mold in the form of dots or sheets, and then A composite material of a predetermined size, which is made by bonding a skin material to a polyolefin resin foam, is supplied in a heated state and pressurized in that state to integrate the thermoplastic resin for aggregate into the composite material by heat fusion. This is a molding method. As the material for this polyolefin resin foam, it is preferable to use a polypropylene resin copolymerized with 0.5 to 35% ethylene in a random, block, or random-block shape, but with a density of 0.897 to 0.955 g/cc. Polyethylene resins with an MI of 0.5 to 50, copolymerized polyethylene resins of ethylene and α-olefin, polyethylene resins copolymerized with ethylene and monomers such as vinyl acetate, acrylic acid, and acrylic esters, as well as those mentioned above. A foam made of a mixture of a polypropylene resin and a polyethylene resin, or a copolymerized polyethylene resin can be used. Furthermore, other resins may be mixed with the above-mentioned resins as long as they do not adversely affect the foam. For example, low-density, medium-density or high-density polyethylene, a polyethylene copolymer copolymerized with α-olefin, or a copolymer containing ethylene as a main component with vinyl acetate or acrylic ester may be mixed. . As the skin material to be attached to the polyolefin resin foam of the present invention, known materials such as fabrics made of natural or artificial fibers, sheets made of polyvinyl chloride resin, thermoplastic elastomer sheets, leather, etc. may be used. I can do it. As the thermoplastic resin for aggregate used in the present invention,
Although it is preferable to use polypropylene resin, materials similar to those of the polyolefin resin foam described above, ABS resin, polyethylene resin, etc. can be used. Furthermore, as a combination of polyolefin resin foam and thermoplastic resin for aggregate, polypropylene resin foam and polypropylene resin are preferred, but polyethylene resin foam and polyethylene resin may also be used. Different materials such as foam and polyethylene resin may be combined. However, when combining different materials, for example, use Admer Film (manufactured by Mitsui Oil Co., Ltd.) or Cranbetter (manufactured by Kurashiki Boseki Co., Ltd.) between them.
Heat-sealed with an adhesive film such as The gel fraction of the polyolefin resin foam used in the present invention is 35% or more, and preferably 46% or more in order to suppress melting and destruction of bubbles. If the gel fraction is less than 35%, bubbles will break due to the heat and pressure during molding, resulting in unevenness on the skin material side. Note that the gel fraction of the polyolefin resin foam mentioned above refers to a value measured as follows. First, cut the foam into approximately 1 mm squares, collect approximately 0.1 g, and accurately weigh this as a sample.
(g). This sample is heated in tetralin at a temperature of 130° C. for 3 hours, then cooled, washed with acetone and then water to remove the eluted matter, and then dried.
Accurately weigh this dried sample and calculate its weight as B (g)
shall be. The gel fraction (%) is calculated using the following formula. Gel fraction (%) = B/A x 100 Furthermore, the difference in the average expansion ratio between the thickness of 0.5 mm from the surface on each of both sides of the polyolefin resin foam is 2 to 20 times. If it is less than 2 times, unevenness will occur on the skin material side, while if it exceeds 20 times, deformation such as warping will occur due to the difference in the degree of shrinkage accompanying cooling after molding. The polyolefin resin foam used in the present invention may be one using a pyrolyzable blowing agent, but the polyolefin resin foam may be prepared by kneading a liquid and a polyolefin resin in an extruder.
It may be produced by a method called extrusion foam obtained by gasifying the liquid, and any known method for producing a crosslinked polyolefin resin foam may be used. A material having an average expansion ratio of 5 to 40 times is preferably used. Particularly preferred methods include a method in which a mixture consisting of a polyolefin resin, a blowing agent, and a crosslinking accelerator is crosslinked with ionizing radiation, and then foamed by heating to a temperature higher than the decomposition temperature of the blowing agent; Examples include a method in which a mixture of an organic peroxide, a crosslinking accelerator, and in some cases a crosslinking regulator is heated to a temperature higher than the decomposition temperature of the organic peroxide and the blowing agent to effect crosslinking and foaming. These methods are suitable for producing endless continuous sheet foams. As the blowing agent, any compound that is liquid or solid at room temperature and that decomposes or vaporizes when heated above the melting point of the polyolefin resin can be used as long as it does not substantially interfere with sheet formation or crosslinking reactions. , those with a decomposition temperature in the range of 180 to 240°C are preferred. Specific examples include azodicarbonamide, azodicarboxylic acid metal salts, dinitrosopentamethylenetetramine, and the like. These blowing agents are suitable for polypropylene resins.
It is used in a range of 0.1 to 40% by weight, and the mixing amount can be changed arbitrarily depending on the type and expansion ratio. When using an organic peroxide in the crosslinking reaction, it is preferable that the decomposition temperature is higher than the flow initiation temperature of the polyolefin resin used in the present invention, and the decomposition temperature is higher than about 120°C when the decomposition half-life is 1 minute. ,
Particularly preferred is a temperature of 150°C or higher. Specific examples thereof include methyl ethyl ketone peroxide (182°C), t-butylperoxyisopropyl carbonate (153°C), and dicumyl peroxide (171°C). These organic peroxides are used in an amount of 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on the polyolefin resin. Typical examples of crosslinking accelerators include divinylbenzene, diallylbenzene, divinylnaphthalene, etc., and the preferred amount added is 0.1 to 30% by weight, more preferably 0.3 to 20% by weight, based on the polyolefin resin. . The polyolefin resin, the blowing agent, the crosslinking accelerator, and the organic peroxide can be mixed by a conventionally known mixing method. For example, mixing with a Henschel mixer, mixing with a Banbury mixer, mixing with a mixing roll, mixing with a kneading extruder,
There are methods such as immersing polypropylene resin in a solution containing a blowing agent, a crosslinking accelerator, and an organic peroxide, which can be used alone or in combination. Particularly when the resin is in powder form, powder mixing using a Henschel mixer is convenient. Powder mixing is usually carried out between room temperature and the softening temperature of the resin, and melt mixing is usually carried out between the melting temperature of the resin and 185°C. When producing a foam in the form of a continuous sheet, it is desirable to form the foam into a sheet by extrusion at a temperature below the decomposition temperature of the foam. Crosslinking and foaming of a foaming composition that has been uniformly mixed or kneaded is 130 to 300% when using an organic peroxide.
It can be carried out by heating at a temperature range of 150 to 260°C, preferably at normal pressure or under pressure. If crosslinking and decomposition of the foaming agent occur almost simultaneously during heating, a method is used in which the mold is heated for the time necessary for crosslinking and foaming in a pressure-sealable mold, and the pressure is removed and foaming is simultaneously performed. This method is extremely effective when foaming a powder mixture as it is. If the foaming agent does not decompose under heat crosslinking conditions, a method is used in which, after crosslinking, the material is heated at normal pressure or under increased pressure at a temperature higher than the decomposition temperature of the foaming agent. In particular, in order to obtain a foam with fine cells, a method of foaming under pressure is preferred. The heating time required for crosslinking and foaming varies depending on the composition heating temperature, the thickness of the material to be foamed, etc., but is usually 1 to 30 minutes. When crosslinking the foamable composition by irradiating it with ionizing radiation, the ionizing radiation is preferably an electron ^beam from an electron beam accelerator or α, β, or γ rays from other radioactive isotopes. , X-rays and ultraviolet rays may also be used. These radiation doses vary depending on the type of crosslinking accelerator and the desired crosslinking ratio, but are generally 0.1 to 30 Mrad, preferably 0.5
~20 Mrad. The foaming of the radiation-crosslinked resin in this way is controlled at the melting temperature of the polypropylene resin, preferably
If the method involves heating to a temperature of 190℃ or higher, normal pressure,
The conditions may be either pressurized or reduced pressure, and as in the case described above, any heating source or heating medium can be used depending on the shape of the unfoamed molded product and the pressure state during foaming. As a means of making a difference in the average expansion ratio on both sides of the polyolefin resin foam, using a foaming machine,
When foaming a foam sheet at a temperature higher than the decomposition temperature of the blowing agent, the heating temperature for one side is lower than that for the other side to reduce the decomposition of the blowing agent and the melting stress of the polyolefin resin. Differences can be created by adjusting or changing the degree of crosslinking reactivity on both sides. Further, polyolefin resin foams having different average expansion ratios can be obtained by integrating them with an adhesive or preferably by heat fusion. [Function] The side of the polyolefin resin foam with a low average expansion ratio and small air bubbles is brought into contact with the molten thermoplastic resin for aggregate, while the side with a high average expansion ratio and large air bubbles is brought into contact with the molten aggregate thermoplastic resin. The side surface is located on the side opposite to the molten aggregate thermoplastic resin and on the side bonded to the skin material, and molded while being integrated by heat fusion. [Example] Example As shown, apparent density 0.050 g/cm ³ (overall average expansion ratio 20 times), thickness 3.0 mm, gel fraction 55%
And, the apparent density of the thickness part up to 0.5mm from one surface of both sides is 0.045g/cm ³ (average foaming ratio 22 times), and the apparent density of the thickness part up to 0.5mm from the other surface is 0.0625 g/cm ³ (average foaming ratio
16 times) on the side with a higher average expansion ratio of the cross-linked polypropylene resin foam 1, as a skin material.
A composite material 3 is constructed by bonding 0.45 mm soft polyvinyl chloride sheets 2 together using a two-component polyester adhesive. Polypropylene resin as a thermoplastic resin for aggregate was melted at a temperature of 195°C and extruded in an amount of 56 g onto the pressing surface of a mold using the T-die method.
The composite material 3 was placed on the polypropylene resin so that the surface of the cross-linked polypropylene resin foam 1 with the lower average expansion ratio was in contact with the polypropylene resin, and the composite material 3 was pressed to 50, 100, 200 kg/cm using a 26 ton press heated to 40°C. By applying a pressure of ² and integrally molded, a vehicle interior molded product 5 in which the aggregate 4 was heat-sealed to the composite material 3 was obtained. Comparative Example 1 Contrary to the above example, a skin material was attached to the side of the crosslinked polypropylene resin foam with a lower average expansion ratio, and on the other hand, a skin material was attached to the side with a higher average expansion ratio in the same manner as in the above example. A vehicle interior molded product was obtained by integrally molding polypropylene resin while heat-sealing it. Comparative Example 2 Using a commercially available product in which the difference between the average expansion ratio of one side of a crosslinked polypropylene resin foam and the average expansion ratio of the other side is less than 2 times, and there is almost no difference.
A skin material was bonded to one side of the surface, and polypropylene resin was integrally molded while being heat-sealed in the same manner as in the previous example to obtain a vehicle interior molded product. When the state of unevenness on the surface of the skin material of each of the above Examples, Comparative Example 1, and Comparative Example 2 was observed, the results shown in the following table were obtained.

[Table] From the above results, the vehicle interior molded product according to the example of the present invention can be obtained even with a 200Kg/cm ² press, whereas in Comparative Example 1, the product can be obtained by pressing at most 50Kg/cm2. cm ² , it is not possible to apply pressure exceeding that, the fusion between the composite material and the polypropylene resin as aggregate is weak, and depending on the application, it is not possible to obtain a product, and Comparative Example 2
It was clear that no product could be obtained. [Effects of the Invention] According to the vehicle interior molded product according to the present invention, the average expansion ratio of the 0.5 mm thick portion from the surface of the polyolefin resin foam is made to differ between one side and the other side, The side with a lower average expansion ratio, that is, the side with smaller bubbles, is brought into contact with the molten aggregate thermoplastic resin and integrally molded using the hot stamping mold method. Even if heat is transferred to the foam, the bubbles at the contact surface where the heat is transferred are small, and even if the bubbles expand due to heat, it is difficult to destroy the bubbles, and even if the bubbles are destroyed, other It is difficult for the surface of the skin material to be affected by air bubbles, and the occurrence of unevenness on the surface of the skin material can be prevented, and both the product yield and quality can be improved. Furthermore, since it is not necessary to mold the composite material or aggregate in advance, production can be performed with fewer steps and productivity can be improved. Furthermore, compared to the conventional vacuum compression molding method, since no adhesive is used during molding, the cost is lower, and there is no risk of environmental deterioration or fire, making it possible to safely obtain molded vehicle interior parts. There are advantages that can be achieved.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of one embodiment of the vehicle interior molded product according to the present invention. 1... Polypropylene resin foam, 2... Skin material, 3... Composite material, 4... Aggregate.

Claims (1)

[Claims] 1 A polyolefin resin foam with a gel fraction of 35% or more, in which the average expansion ratio of the thickness up to 0.5 mm from the surface on each side of the foam is greater than that of the other, and the expansion ratio of both is greater than that of the other. A skin material is bonded to the side of the polyolefin resin foam with a difference in magnification of 2 to 20 times, the side having a higher average expansion ratio, while the surface material has a lower average expansion ratio,
A vehicle interior molded product made by integrally molding aggregate thermoplastic resin using the hot stamping molding method.