JPS6111191B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a thermoplastic resin foam board. More specifically, the present invention relates to a method for producing a thermoplastic resin foam board that has the properties of polyolefin resins such as elasticity, impact resistance, and solvent resistance, and has excellent shape retention. Conventionally, as a manufacturing method for expanded polystyrene plates,
A known method is to extrude polystyrene particles containing a blowing agent from a cylindrical mold and cut open the resulting cylindrical foam to obtain a plate-shaped molded body. but,
The polystyrene plate obtained in this manner has a limited thickness, and has the disadvantage that it retains distortion as a cylindrical foam and is easily warped. Therefore, a method is known in which a cylindrical foam after extrusion is compressed using pinch rolls to fuse the inner surface to obtain a foamed polystyrene plate (fused plate) that does not cause warpage, and various extrusion manufacturing methods are used. It has been proposed and implemented.
This method has the advantage that a relatively thick foam board can be obtained in one step. However, although the thus obtained fused thick foamed styrene plate has good shape retention, it is not suitable for fields where elasticity, impact resistance, solvent resistance, etc. are required. On the other hand, it is known that foams of polyolefin resins such as polyethylene and polypropylene are superior to foamed polystyrene in terms of elasticity, impact resistance, and solvent resistance as described above. Therefore, it is conceivable to use polyolefin resin as a material and create a thick foam board by fusing the inner surface to take advantage of its advantages, but according to the research of the present inventors, polyolefin resin containing a foaming agent Even when the resulting cylindrical foam was extruded from a cylindrical mold under various conditions in the same way as polystyrene, and the resulting cylindrical foam was compressed, a good fused plate could not be obtained. This is because styrene resins such as polystyrene are sufficiently fused by narrow pressure even at the temperature after foaming, but in the case of polyolefin resins, fusion is achieved at the inner temperature of the cylindrical foam after foaming. This is because it is not done enough. For this reason, it may be possible to raise the extrusion temperature of the polyolefin resin foam to raise the inner surface temperature to a temperature at which welding is possible, but in this case, the foamed cells themselves are unstable and easily disappear, and the inner surface of the foam melts. Even though the adhesion was good, the foaming ratio was extremely low and the desired foamed molded board could not be obtained. As described above, it has been extremely difficult to manufacture thick foam boards made of polyolefin resin with good elasticity, impact resistance, and solvent resistance by fusion bonding. In view of the above points, the inventors of the present invention have developed a fusion plate using thermoplastic resin particles obtained by crosslinking and grafting polyolefin resin particles in a specific amount with a specific amount of vinyl aromatic monomer. It has been discovered that a thermoplastic resin foam board with good elasticity, impact resistance, and solvent resistance can be obtained by manufacturing the same, and the present invention has been achieved. Thus, according to the present invention, 10 to 70 parts by weight of polyolefin resin particles and 90 to 30 parts by weight of a vinyl aromatic monomer are suspended in an aqueous medium, and this is subjected to polymerization conditions in the presence of a catalyst. After crosslinking and graft polymerizing thermoplastic resin particles with a gel concentration of 30 to 80% to a polyolefin resin, supplying the particles and a blowing agent to an extruder, and heating, melting, and kneading in the extruder,
Provided is a method for producing a thermoplastic resin foam board, which comprises extruding the foam through a cylindrical mold to form a cylindrical foam, compressing it with pinch rolls to fuse the inner surfaces to obtain a two-ply thermoplastic resin foam board. Ru. Examples of the resin of the polyolefin resin particles used in this invention include ethylene homopolymers and copolymers mainly composed of ethylene such as ethylene-vinyl acetate, ethylene-vinyl chloride, and ethylene-methyl methacrylate. These polyolefin resin particles are usually used in the form of particles such as spheres or pellets, and the particle size is preferably 6 to 30 mesh. Examples of the vinyl aromatic monomer used in this invention include styrene, methylstyrene, halogenated styrene, etc. In addition to these, α-methylstyrene can be copolymerized with a vinyl aromatic monomer containing 50% by weight or more of these monomers. , a mixture with monomers such as methyl methacrylate, divinylbenzene, dimethyl maleate, etc. are used. In this invention, polyolefin resin particles are suspended in an aqueous medium together with a vinyl aromatic monomer. For suspension, the amounts used are 10 to 70 parts by weight of the polyolefin resin particles and 90 to 30 parts by weight of the vinyl aromatic monomer, based on a total of 100 parts by weight of the resin and monomer. If the amount of polyolefin resin particles is less than 10 parts by weight, the desired elasticity, impact resistance, and solvent resistance will be insufficient, and if it is more than 70 parts by weight, the final foamed molded plate will be too flexible and will not adhere properly. It is undesirable due to its inferior properties and shape retention. It is preferable to use 25 to 70 parts by weight of polyolefin resin particles and 75 to 30 parts by weight of vinyl aromatic monomer, since the advantages of each resin can be best utilized. Further, the polyolefin resin and the vinyl aromatic monomer are suspended in an aqueous medium using a dispersant. The dispersant usually includes polyvinyl alcohol,
Methyl cellulose, calcium phosphate, magnesium pyrophosphate, etc. are used, and the appropriate amount is 0.01 to 5 parts by weight based on water. As a specific suspension method, for example, polyolefin resin particles are suspended in an aqueous solution containing a dispersant, and then the vinyl aromatic monomer is added to the suspension in its entirety or divided into portions to increase the amount. It is done. By this operation, the vinyl aromatic monomer is absorbed into the polyolefin resin particles. The suspension may be warmed during operation. In this invention, a catalyst is added and used in order to crosslink and graft polymerize the absorbed vinyl aromatic monomer to the particles in the polyolefin resin. Examples of the catalyst include di-
tert-butyl peroxide, benzoyl peroxide, lauroyl peroxide, oleyl peroxide, tolyl peroxide, di-tert-butyl diperphthalate, tert-butyl peracetate, tert-butyl perbenzoate, dicumyl peroxide, tert-butyl peroxide isopropyl carbonate, 2,5-dimethyl-2,5-
Di(tert-butylperoxy)hexane, 2,5
-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, tert-butyl hydroperoxide, cumene hydroperoxide, p-pentane hydroperoxide, cyclopentane hydroperoxide, cyisopropylbenzene hydroperoxide, p-tert-butyl Cumene hydroperoxide, pinane hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, etc. or mixtures thereof can be mentioned. The appropriate amount of these additives to be added is 0.2 to 2.0% by weight based on the polyolefin resin in order to obtain a specific gel concentration as described below. The catalyst may be added in the form of a solution of a solvent (for example, toluene, benzene, etc.) to the catalyst solution of polyolefin resin particles obtained by absorbing the vinyl aromatic monomer obtained above. It may also be dissolved in the preceding vinyl aromatic monomer. By subjecting the suspension to which the catalyst has been added to known polymerization conditions, such as elevating the temperature to a temperature at which vinyl aromatic monomers can be polymerized, crosslinking and grafting of the polyolefin resin with vinyl aromatic monomers can be achieved. At the same time, thermoplastic resin particles in which the vinyl aromatic polymer is uniformly filled in the polyolefin resin particles are obtained. In this invention, the degree of crosslinking and grafting of the thermoplastic resin particles is adjusted so that the gel concentration relative to the polyolefin resin particles is 30 to 80%. However, the gel concentration (%) is expressed as a percentage of the dry weight of the boiling toluene insoluble matter relative to the weight of the polyolefin resin in the thermoplastic resin particles. A low gel concentration means that there are few crosslinked products and graft copolymers of the polyolefin resin, whereas a high gel concentration means that there are many crosslinked products and graft copolymers of the polyolefin resin. If the gel concentration is less than 30%, the polyolefin resin and vinyl aromatic polymer will undergo phase separation during the extrusion process, making it impossible to obtain a cylindrical foam with uniform cells. In this case, the viscosity of the molten resin in the extruder increases, making extrusion difficult, and even if the extrusion temperature is raised, phase separation and foaming agent dissipation occur, making it impossible to obtain the desired foam. The desired gel concentration is adjusted by adjusting polymerization conditions such as the amount of catalyst, reaction temperature and time. After separating and drying the thermoplastic resin particles obtained in this way from the aqueous medium, they are supplied together with a foaming agent to an extruder 1, where they are heated, melted and kneaded, and then extruded through a cylindrical mold 2 to form a cylindrical foam 4, which is then pinched. roll 6
The foamed fused plate of the present invention can be obtained by compressing the foamed material. The extrusion conditions in this case may be carried out in accordance with the manufacturing conditions of ordinary polystyrene foam fused plates, and at least a step of compressing the cylindrical foam with pinch rolls or the like while the inner surface temperature is still above the softening temperature may be performed. Bye. The inner surface of the cylindrical foam according to the present invention can be easily fused by narrow pressure if it is above the softening temperature. Furthermore, the foamed cells are well maintained even at that fusion temperature. In addition, in the process in which the cylindrical foam extruded from the annular slit of the cylindrical mold into the reduced pressure area is compressed and fused by pinch rolls,
To prevent the cylindrical foam from deforming, creating weld lines and uneven thickness, the outer periphery of the cylindrical foam was blown with air (3) or cooled with a cooled surface. It is usually desirable to maintain the shape of the cylindrical foam, such as by contacting the inner surface of the cylinder. The blowing agents used in this invention include aliphatic hydrocarbons such as propane, butane, bentane, and hexane, cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane, methyl chloride, ethyl chloride, dichlorodifluoromethane, chlorodifluoromethane, and trichloromethane. Volatile blowing agents such as fluoromethane, halogenated hydrocarbons such as methylene chloride and azodicarbonamide, N,
Separate blowing agents such as N'-dinitrosopentamethylenetetramine can be mentioned. These blowing agents are usually press-fitted or added into an extruder together with the thermoplastic resin particles, but they may be used by being impregnated or mixed with the thermoplastic resin particles in advance. The amount of the blowing agent used varies depending on the resin, the type of blowing agent, and the desired expansion ratio, but is usually about 1% by weight based on the thermoplastic resin particles. In addition to the blowing agent, appropriate amounts of various auxiliaries and additives such as perlite, liquid paraffin, baking soda, citric acid, talc, pigments, dyes, and flame retardants may be supplied to the extruder. The foaming ratio of the thermoplastic resin foam board thus obtained is about 3 to 20 times, and the thickness thereof is usually 3 mm or more. Since the thermoplastic resin foam board manufactured by the method of the present invention is made of polyolefin resin, it has excellent elasticity, impact resistance, solvent resistance, etc. Furthermore, the rigidity and shape retention, which are insufficient with polyolefin resins alone, are significantly improved by the use and treatment of vinyl aromatic monomers. Furthermore, since the foam board has skins on both sides, it has high surface strength and good dimensional accuracy. Therefore, it can be adapted to various uses and is also suitable for secondary molding processing. According to this invention, a thick thermoplastic resin foam board that retains the properties of polyolefin resin can be obtained in one step with good extrusion processability, and it also has a smooth surface that cannot be obtained by slicing a low foam board or using the T-die method. A thermoplastic resin foam board with good dimensional accuracy can be obtained in one step, which is very advantageous industrially. Next, this invention will be explained in more detail with reference to Examples. Note that all parts and percentages are by weight. Example 1 (A) Production of thermoplastic resin particles Magnesium pyrophosphate 0.9
and sodium dodecylbenzenesulfonate
Dissolve 0.04 parts in 200 parts of water, add 80 parts of polyethylene resin to disperse, heat this to 80℃,
To this, a mixture of 120 parts of styrene monomer, 1 part of benzoyl peroxide and 1 part of dicumyl peroxide was gradually added over 6 hours. After the addition was completed, the reaction solution was heated to 90°C for 2 hours, and then
The temperature was raised to 130°C and polymerization and crosslinking reactions were carried out for 4 hours. Then, the reaction solution is cooled to separate the polymer,
The particles were washed with water and dried to obtain 200 parts of thermoplastic resin particles consisting of 40% polyethylene resin component and 60% polystyrene resin component, in which both resin components were uniformly mixed and partially crosslinked and graft polymerized. The gel percentage of this particle was 50%. Table 1 below shows examples in which the type of resin, amount of added substance, and addition time were changed in the same manner as in Example (A) above. In addition, comparative examples are also illustrated for reference.

[Table] (B) Production of foam board Thermoplastic resin obtained in the above example (A) as resin
To 100 parts, 0.1 part of liquid paraffin and 1.0 part of talc were added and thoroughly mixed in a tumbler, and this mixture was supplied to an extrusion device with a screw diameter of 65 mm.
Butane was press-injected as a foaming agent into the extrusion device at a ratio of 3.3 parts to 100 parts of the resin, and the mixture was thoroughly melted and kneaded. The extrusion temperature was 110°C to 230°C. A homogeneous mixed molten resin containing butane is pumped through an annular slit with a diameter of 110 mm and a slit width of 2.0 mm provided in a cylindrical mold attached to the tip of the extrusion device.
It is extruded into the atmosphere at a rate of kg/hour and foamed.
A cylindrical foam with a circumference of 900 mm was obtained. This cylindrical foam was compressed using pinch rolls to fuse the inner surfaces to form a two-layer foam board. This foam board is thick
10mm, width 450mm, density 0.095g/cc, the surface has uniform bubbles and no irregularities, and it looks like a piece of unfoamed polyethylene film that is produced when polyethylene resin and polystyrene resin phase separate. There were no apparent defects in appearance (temporarily called keloid conditions), and the two sheets were well fused and firmly integrated. Next, for comparison, the resin used is the comparative example mentioned above.
When the resin obtained by method (H) was extruded under exactly the same conditions as in the previous method, the extrusion power load was high and extrusion became difficult, so the overall temperature condition was raised by about 8°C. As a result, I was able to obtain a foam board. This foam board has a wall thickness of 8.5
mm, width 430 mm, and density 0.12 g/cc, and although no keloid was observed on the surface, it was highly uneven and could hardly be called a good foam board. Similarly, while changing the extrusion molding conditions slightly,
The results for the various resins described in A to L above are shown in Table 2.

【table】 [Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a sectional view of a thermoplastic resin foam board obtained by the method of the present invention. 1... Extruder, 2... Cylindrical mold, 3... Air ring, 4... Cylindrical foam, 5... Guide plate, 6... Pinch roll, 7... Pulling machine, 8... Cutting machine.

Claims (1)

[Claims] 1. 10 to 70 parts by weight of polyolefin resin particles;
90 to 30 parts by weight of a vinyl aromatic monomer are suspended in an aqueous medium and subjected to polymerization conditions in the presence of a catalyst to give a gel concentration of 30% to a polyolefin resin.
~80% cross-linked and graft-polymerized thermoplastic resin particles, feeding the particles and a blowing agent to an extruder,
It is characterized by heating, melting, and kneading in an extruder, extruding it through a cylindrical mold to form a cylindrical foam, and compressing it with pinch rolls to fuse the inner surfaces to obtain a two-ply thermoplastic resin foam board. Method for manufacturing thermoplastic foam board. 2. The manufacturing method according to claim 1, wherein the polyolefin resin is an ethylene homopolymer or a copolymer mainly composed of ethylene. 3. Claim 1, wherein the vinyl aromatic monomer is styrene, methylstyrene, ethylstyrene, halogenated styrene, or a mixture of a vinyl aromatic monomer containing 50% by weight or more of these monomers and a copolymerizable monomer. Or the manufacturing method described in item 2.