JPS637150B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a multilayer structure that has excellent waterproofness, abrasion resistance, and overall rigidity. Currently, the main material for pallets is wood,
Wooden pallets have many problems, such as corrosion, laminated bags breaking due to wood, nails, etc., increased weight due to absorption of moisture, easy breakage, and unsanitary conditions. To solve this problem, we used a plywood board as a core material, covered the front and back sides of this core material with glass fiber reinforced resin (hereinafter referred to as FRP) using an isocyanate adhesive, and used the sandwich structure as a deck board. Pallets have been proposed, but their slippery surfaces pose operational and safety problems during empty transport. On the other hand, in order to prevent this slippage, the surface of the polyethylene deck board has a concave and convex pattern, and
A pallet has been proposed in which a rubber sheet is partially pasted with an isocyanate adhesive or vinyl acetate latex on a portion of the surface of the deck board and the back surface of the deck board where the claws of a forklift come into contact to prevent slipping. However, although this plastic pallet has solved the problem of slipperiness and waterproofness, it has problems with load bearing capacity, and when a heavy load is loaded, the load may collapse due to deflection. In order to improve the shortcomings of these conventional pallets, the present applicant has developed a skin layer made of a rubber material, a core material layer made of wood, stone, metal, etc. having a predetermined rigidity, and a thermosetting material for the textile base material. A multilayer structure characterized in that a laminate is formed by placing and laminating a back-up layer made of sheet-like preformed material (SMC) impregnated with resin, and the laminate is integrally molded by heating and compression. An application was filed for the manufacturing method (Japanese Patent Application Laid-Open No. 1983-1999).
No. 110691). In this manufacturing method, a laminate formed from the above-mentioned rubber skin layer, core material layer and backup layer (SMC),
By simultaneously heating and compressing, there is no need for an adhesive, and each layer can be integrated in a single compression process, making it possible to reduce costs by shortening the process. Furthermore, the multilayer structure manufactured by this method has excellent surface waterproofness and frictional properties, and has sufficient overall rigidity, making it ideal for use as a pallet deck board. However, when using a material containing about 0.5 to 10% moisture at room temperature, such as particle board, plywood, or cardboard made of pulp paper, as the core material,
Normal SMC compression molding conditions, i.e. temperature 120~
Under conditions of 160℃ and a pressure of 15 to 150 Kg/ ^cm2 , the crosslinking time of the crosslinkable rubber sheet is longer than the curing time of SMC (usually 6 to 12 minutes), and the moisture in the core material is generated as water vapor, resulting in a product. They often become swollen and have a negative impact on us. It is possible to use a mold with gas vent holes to dissipate the generated water vapor, but the unsaturated polyester resin that makes up SMC flows into the gas vent holes due to the pressure applied during compression molding, and hardens there. The gas vent hole may be blocked, and the water vapor that has no place to escape will cause blisters or cracks in the core material of the molded product, resulting in a product with poor practicality. In order to improve this drawback, it is conceivable to pre-dry the water-containing core material before use in molding, but it is not economically advisable for a processing company to newly install such drying equipment. The present invention solves these drawbacks when using a water-containing core material, even if SMC's unsaturated polyester resin enters the gas vent hole of the mold during compression molding, the rubber crosslinks during the time until water vapor is generated. The problem can be solved by crosslinking the rubber and curing the SMC, or by crosslinking the rubber and curing the SMC before the internal pressure reaches enough to deform the resulting multilayer composite structure even if water vapor is generated. This objective can be achieved by using a crosslinkable rubber sheet that can be crosslinked in 1 to 5 minutes, preferably 1 to 3 minutes. That is, in the present invention, a sheet molding compound is placed and laminated on at least one side of a water-containing core material such as wood or cardboard, and a crosslinkable rubber sheet is further placed on the surface of this sheet molding compound. In a method of manufacturing a multilayer composite structure in which a crosslinked rubber sheet, a glass fiber reinforced resin, and a core material are integrated by heating and compression molding the laminated laminate, the crosslinkable rubber sheet has an ethylene content of 30 to 75% by weight. %
For 100 parts by weight of ethylene-propylene copolymer rubber having a Mooney viscosity ML ₁₊₄ (100°C) of 10 to 150, 1 to 10 parts by weight of organic peroxide and acryloyloxy and/or methacryloyl A compound having at least two or more oxy groups
The present invention provides a method for producing a multilayer composite structure, characterized in that it is formed from a composition blended in a proportion of 0.005 to 0.2 moles. In the practice of the present invention, water-containing core materials include, to some extent, plywood, soft or hard fiberboard, particle board, asbestos slate board, gypsum board, asbestos cement board, corrugated paper, cardboard paper, etc. stiffness (specifically, the bending modulus of
_* 1000 Kg/cm ² ) or more, and porous ones that allow the thermosetting resin liquid to penetrate and impregnate to some extent through the surface, or those that have irregularities on the surface. * [Wood - Japanese Agricultural Standards (Ministry of Agriculture and Forestry Notification No. 932), Asbestos Slate - JISA1408 Bending Test Method for Architectural Boards]. Among these, wood materials with high impact resistance are preferred. And, as a sheet molding compound (SMC), “FRP - Production and Technology -
(Published by Plastics Age Co., Ltd. on December 10, 1973)
Usually commercially available as described on pages 148-153 of
SMC, Patent Application No. 54-134643, No. 54-152301,
SMC for low pressure molding disclosed in Japanese Patent No. 55-62642 and Japanese Patent No. 55-86088 can be used. In general, SMC is made by impregnating a nonwoven or woven fabric base material made of inorganic fibers (glass fibers, asbestos fibers, etc.) or organic fibers (thermoplastic polyester fibers, etc.) with a liquid unsaturated polyester resin composition having the following composition. It is a sheet-like material obtained by thickening a resin so that it can be carried and cut into any shape, and can be molded into any shape by placing it in a compression mold and applying heat and pressure. Unsaturated polyester resin composition (A) Unsaturated polyester 30 to 80 parts by weight (B) Vinyl monomer mainly composed of styrene
70-20 parts by weight (C) Polymerization initiator 0.01-5% by weight of the sum of (A) and (B) (D) Thickener 0.1-2% by weight of the sum of (A) and (B) (E) Radical-absorbing compound 0 to small amount The following may be added to the above composition as necessary. Filler: Talc, calcium carbonate, silica, diatomaceous earth, mica, aluminum hydroxide Mold release agent: Zinc stearate, stearic acid, aluminum stearate Pigment: Titanium oxide, carbon black, red iron oxide, cadmium yellow Shrinkage prevention agent: Polyacrylic acid, polystyrene,
Particles such as styrene-maleic acid copolymer. The unsaturated polyester of (A) above may be made of, for example, an unsaturated polybasic acid such as maleic anhydride, fumaric acid, itaconic acid, etc., and a polyhydric alcohol such as ethylene glycol, propylene glycol, diethylene glycol, etc., and if necessary, phthalic anhydride. By blending saturated polybasic acids such as acid, isophthalic acid, and adipic acid,
Obtained by reaction. Further, examples of vinyl monomers other than styrene include vinyltoluene, chlorostyrene, methylstyrene, methyl methacrylate, and the like. Furthermore, the polymerization initiator has a temperature of 72.5°C to 104°C to obtain a half-life of 10 hours,
The temperature at which unsaturated polyester resin containing 1 part by weight of the polymerization initiator per 100 parts by weight of the total of unsaturated polyester and vinyl monomer gels in 15 minutes is
Preferably, the temperature is 71°C to 95°C. Such a polymerization initiator (the temperature in parentheses indicates a half-life of 10 hours) is diacyl peroxide-based benzoyl peroxide (74°C) or peroxy ester-based t-butylperoxy-2-ethylhexanoate. (72.5°C), t-butyl peroxybenzoate (104°C), etc., especially benzoyl peroxide, t-butylperoxybenzoate (104°C), etc.
-Butyl peroxybenzoate is preferred. As the thickener, magnesium oxide, magnesium hydroxide, calcium oxide, and calcium hydroxide may be used alone or in combination of two or more. Although it is extremely rare, a polymerization inhibitor may be added in an amount of 30 p.pm or less of the sum of unsaturated polyester and vinyl monomer such as styrene in order to adjust the gelation time of SMC. Examples of such polymerization inhibitors include hydroquinone, benzoquinone, mono-t-butylhydroquinone, and catechol. Furthermore, ethylene, which constitutes the crosslinkable rubber sheet,
The propylene copolymer rubber has an ethylene content of 30 to 75% by weight, a propylene content of 70 to 25% by weight, and if necessary, a copolymer of dienes such as ethylidenenorbornene and dicyclopentadiene in a proportion of 5 to 30% by weight. Ethylene/propylene copolymer rubber with an ioso value of 12 to 20.
Examples include diene terpolymer rubber. The Mooney viscosity ML ₁₊₄ (100℃) of these rubbers is 10
-150, preferably 30-110. In addition, examples of crosslinking agents made of organic peroxides include benzoyl peroxide, t-butylperoxy-
2-Ethylhexanoate, t-butylperoxybenzoate, dicumyl peroxide, lauroyl peroxide, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)- Examples include 3,3,5-trimethylcyclohexanone and t-butylperoxymaleic acid. In carrying out the invention,
The polymerization initiator blended into the SMC and the crosslinking agent blended into the crosslinkable rubber sheet may be the same or different, but the curing reaction of the SMC and the crosslinking reaction of the rubber may be started at the same time or one after the other. The difference in decomposition temperature is 0 to 15 to obtain a half-life of 10 hours to strengthen the bond between the crosslinked sheet and FRP.
℃, preferably 0 to 10℃ should be used. Furthermore, an acryloyloxy group and/or
Examples of compounds having at least two methacryloyloxy groups include ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and polyacrylate equivalents thereof. Among these, from the viewpoint of crosslinking speed and physical strength such as tensile strength, elongation, and creep resistance of the resulting crosslinked rubber sheet, difunctional diacrylate or dimethacrylate is preferable to trifunctional or higher functional polyacrylate or polymethacrylate. is preferable. Furthermore, the shorter the chain length between the functional groups, the better, and generally the molecular weight of the compound is preferably about 198 to 400. The most suitable one is ethylene glycol dimethacrylate. Although monomethacrylates such as lauryl methacrylate have the effect of accelerating the crosslinking rate,
This is not preferred because it causes decomposition of the ethylene-propylene copolymer rubber during crosslinking and reduces the mechanical strength of the resulting crosslinked rubber sheet. Additionally, when crosslinking ethylene-propylene copolymer rubber using an organic peroxide, sulfur is added as an auxiliary agent in order to speed up the crosslinking rate. In this case, the crosslinking time of ethylene-propylene copolymer rubber is 5
~12 minutes, and cannot be used in the practice of the present invention. In order to produce a crosslinkable rubber sheet using these, organic peroxide is added in an amount of 1 to 10 parts by weight, preferably 5 to 10 parts by weight, per 100 parts by weight of ethylene-propylene copolymer rubber. The compound having at least two acryloyloxy groups and/or methacryloyloxy groups is 0.005 to 0.2
mol, preferably 0.01 to 0.1 mol, or a composition in which, if necessary, pigments such as carbon black and zinc white, dispersants such as stearic acid, and plasticizers such as process oil are further blended. is produced into a sheet by rolls at a temperature at which the organic peroxide does not decompose, preferably from 30 to 60°C. In order to manufacture the multilayer composite structure of the present invention in which the crosslinked rubber sheet, glass fiber reinforced resin (FRP), and the core material are integrated using these core materials, SMC, and crosslinkable rubber sheets, for example, at least one side of the core material A crosslinkable rubber sheet is placed on the surface of the SMC, and the laminate is then molded into an upper mold configured to match the shape of the final product and a lower mold with gas vent holes. Place it on the lower mold of a compression mold set at a temperature of 140 to 160℃, then clamp it, and
~200℃, preferably 110~170℃, pressure 5~150℃
Kg/ ^cm2 , preferably 5-40Kg/ ^cm2 for 1-5 minutes,
Compression molding is preferably performed for 2 to 4 minutes to cure the unsaturated polyester resin constituting the SMC and to crosslink the crosslinkable rubber sheet, followed by opening the mold and removing the molded product. , remove unnecessary burrs to obtain the desired product. The viscosity decreased due to heating during compression molding.
The unsaturated polyester resin solution that makes up SMC partially penetrates into the core material, impregnates it, or casts it onto the surface of the core material, and during the curing process, the core material and SMC adhere to each other, and each layer is integrated. In addition, the resin solution is also cast on the rubber sheet surface,
The cured product of the resin solution acts as an adhesive to integrate the crosslinked rubber sheet with the FRP. During this compression molding, if the compression molding time from mold clamping to mold opening is long, about 3 minutes or more, the moisture contained in the core material changes to steam and evaporates out of the mold through the gas vent holes. However, in a molding time of 3 to 5 minutes, even if some of this water vapor is trapped within the product, the internal pressure is small and does not cause deformation of the resulting product. In order to facilitate understanding of the present invention, the present invention will be explained below using drawings. Figure 1 shows the state in which the mold is opened after compression molding and the molded product (deck board) A is taken out.
In the figure, 1 is the core material, 2 is the glass fiber reinforced resin cured with SMC, 3 is the rubber sheet crosslinked with the crosslinkable rubber sheet, 4a is the upper mold of the compression mold, and 4b is the lower mold of the lower mold. A gas vent hole 5 is provided in the mold. In the practice of the present invention, the thickness of each layer is 10
~150mm, SMC layer 2~10mm, crosslinkable rubber sheet layer
A thickness of 0.3 to 3 mm is desirable. In the present invention, since the crosslinkable rubber sheet can be crosslinked in an extremely short time (1 to 5 minutes), the molding cycle of the product can be set to 1.5 to 6 minutes, and mass production of the product is possible. Moreover, the obtained product has high dimensional accuracy without warping or sinking. The present invention will be explained in more detail with reference to Examples below. Note that parts and percentages in the examples are based on weight. Example 1 60 moles of phthalic anhydride, 40 moles of fumaric acid, and 100 moles of propylene glycol were added to an autoclave and reacted at 205°C for 6 hours under a nitrogen stream.
26). 70% styrene solution of the above unsaturated polyester
Additives (1) to (4) below were added to 100 parts to prepare a liquid unsaturated polyester resin composition. (1) Filler Calcium carbonate 150 parts Glass fiber 30 parts (2) Hardening agent t-butyl perbenzoate 1 part (3) Thickener MgO 1 part (4) Mold release agent Zinc stearate 2 parts Apply the above on the release film. An unsaturated polyester resin composition is applied, then a 300 g/m ² chopped strand mat is placed on this surface, the unsaturated polyester resin composition is applied again, and a release film is placed on top of it. A laminate was obtained. This laminate is compressed with a roll to impregnate the resin into the mat, defoamed, and then rolled up and cured for one day in an atmosphere of 40°C to form a semi-solid molding sheet (SMC) with a wall thickness of 1.2 mm. ) was obtained. Particle board (thickness: 12 mm, with 4 holes of 50 mm diameter, water content: approximately 10%) is used as a core material, this core material is surrounded by the above SMC, and a crosslinkable sheet made of the following composition is further placed on the top surface. After loading the laminate in which cut pieces of the same crosslinkable sheet were placed on the lower surface of the lower mold (160°C) with gas vent holes, the mold was placed. Tighten,
Compression molded for 2 minutes at a temperature of 160℃ and a pressure of 10Kg/ ^cm2 .
Next, the mold is opened without cooling, and the FRP layer is 0.7 mm.
A molded product with a crosslinked rubber layer of 0.5 mm and a core material layer of 12 mm was obtained. Composition of the crosslinkable rubber sheet (a) 100 parts of ethylene/propylene terpolymer rubber with an ethylene content of 57% and a Mooney viscosity of 38 (iodine number 19) (b) 1,1-bis(t-butyl peroxide) Oxy)-3,
3,5-trimethylcyclohexane 9 parts (c) Pigment 2 parts (d) Ethylene glycol dimethacrylate 5 parts. The adhesion of the skin layer of the obtained molded product was tested in accordance with the peel test method 7 of JIS-K-6301 Vulcanized Rubber Physical Test Method, and the result was 0.5 kg/cm. In addition, in order to confirm the adhesive strength between FRP and particle board, the above molded body was made into a short fence with a width of 20 mm, a length of 240 mm, and a wall thickness of 13.9 mm, and this short fence was used to prevent spans.
When a 190 mm three-point bending test was performed, no peeling between the layers was observed even when the center load was 40 kg. The flexural modulus of the molded product according to JIS-K-6911 was 75000 kg/cm ² . In addition, this molded product has no pinholes or blisters on the crosslinked rubber sheet surface.
Moreover, the core material was excellent in that it did not swell. Examples 2 to 5 Molded products without holes, blisters, or warpage were produced in the same manner as in Example 1, except that the ethylene-propylene copolymer rubber shown in Table 1 was used and the compression molding time was varied. did. The minimum compression molding time for obtaining the molded body is shown in the same table.

[Table] In addition, when 100 units were produced, the number of defective products was 2 or less. Comparative Example 1 Example 1 except that dicumyl peroxide was used instead of 1,1,-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane and sulfur was used instead of ethylene glycol dimethacrylate. Compression molding was carried out in the same manner. In the obtained molded product, the rubber sheet was not sufficiently crosslinked,
It had low mechanical strength. Furthermore, when the compression molding time is set to about 7 minutes, the crosslinking of the rubber is sufficient, but for 100 products
Out of 15 products, defective products with bulges in the core material were found.

[Brief explanation of the drawing]

FIG. 1 shows a state in which the mold is opened after compression molding and the multilayer composite structure is taken out in one embodiment of the present invention. In the figure, 1 is the multilayer composite structure, 1 is the core material, and 2 is the multilayer composite structure.
SMC is a hardened glass fiber reinforced resin, 3 is a crosslinked rubber sheet, and 4a and 4b are molds.

Claims (1)

[Claims] 1. A sheet molding compound is placed and laminated on at least one side of a water-containing core material such as wood or cardboard, and a crosslinkable rubber sheet is further placed on the surface of this sheet molding compound. In a method for manufacturing a multilayer composite structure in which a crosslinked rubber sheet, a glass fiber reinforced resin, and a core material are integrated by heating and compression molding the laminated product placed and laminated, the crosslinkable rubber sheet has an ethylene content of 30 to 30%. 75% by weight
For 100 parts by weight of ethylene-propylene copolymer rubber having a Mooney viscosity ML ₁₊₄ (100°C) of 10 to 150, 1 to 10 parts by weight of organic peroxide and acryloyloxy and/or methacryloyl A compound having at least two or more oxy groups
1. A method for producing a multilayer composite structure, characterized in that it is formed from a composition blended in a proportion of 0.005 to 0.2 mole. 2. The method according to claim 1, wherein the compound having a methacryloyloxy group is ethylene glycol dimethacrylate.