JPS6123222B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a foam molded article. The styrene-maleic anhydride copolymer resin used in this invention has a higher heat distortion temperature than polystyrene, and is expected to be used in various fields requiring heat resistance. However, although the copolymer resin can be made into a foam by extrusion molding, it has been difficult to produce a foam by so-called bead molding. That is, for this reason, it has been proposed to make expandable particles for bead molding by reacting the copolymer resin with a monohydric alcohol (see JP-A-47-39186). However, when pre-expanded, the expandable particles give pre-expanded particles with a relatively low bulk specific gravity, but when these pre-expanded particles are bead-molded, the mold cannot be molded unless the mold is overfilled. . This invention is a foamable copolymer resin in which a compound having at least two active hydroxyl groups is reacted with the acid anhydride group of a styrene-maleic anhydride copolymer resin, and a blowing agent is contained in this modified copolymer resin. This is due to the discovery that by forming particles into particles, it is possible to obtain a foamed molded product with a low specific gravity without overfilling during bead molding, and the resulting foamed molded product has excellent heat resistance. It is. Thus, according to the present invention, a styrene-maleic anhydride copolymer resin is reacted with a hydroxy compound having 2 to 4 active hydroxy groups in an amount of 2.5 to 150 mol% based on maleic anhydride molecules, and the hydroxy compound is volatilized to the resin. The foamed particles are impregnated with a foaming agent to obtain expandable particles, and then the expandable particles are made into pre-expanded particles, and the obtained pre-expanded particles are filled into a mold in an amount equal to or 10% in excess of the capacity of the cavity. The present invention provides a method for producing a foamed molded article, which is characterized in that a foamed molded article having a low specific gravity and good thermal stability is obtained by molding the foamed article. The resin used in this invention is preferably a styrene-maleic anhydride copolymer resin containing 2 to 25% by weight of maleic anhydride obtained by copolymerizing maleic anhydride with styrene and having an average degree of polymerization of 500 to 4,000.
These resins are described, for example, in U.S. Pat.
It can be made by the method disclosed in No. 3509110,
It is available under the name Dilarc (trade name of Alco/Polymers, Inc., USA). The resin can be used in the form of particles such as pellets, granules or special strips. Preferred forms are pellets or beads. The resin pellets can be obtained, for example, by block polymerizing maleic anhydride and styrene in the presence of a catalyst and pelletizing the resulting polymer using an extruder. If the maleic anhydride content is less than 2% by weight, the resin will not have excellent heat resistance, and if it is more than 25% by weight, it will be difficult to impregnate the resin with a blowing agent. Further, if the average degree of polymerization of the resin is less than 500, blocking occurs during impregnation with a blowing agent or the heat resistance becomes poor, and if it is more than 4,000, brittleness increases, making it undesirable as a foamed molded product. More preferred copolymer resin particles of the present invention have a maleic anhydride content of 5 to 15% by weight and an average degree of polymerization of 900 to 2,000. When producing expandable particles using the above styrene-maleic anhydride copolymer resin particles, the copolymer resin particles are suspended in an aqueous medium. The weight ratio of the copolymer resin to the aqueous medium used during suspension is selected to be around 1:1 in the case of a small scale, but in the case of an industrial scale,
Although the weight ratio used can be 1:0.7 to 5, it is preferable to reduce the amount of the aqueous medium used to the utmost. The aqueous medium consists of water and a suitable amount of dispersant. Examples of the dispersant include organic compounds such as partially saponified polyvinyl alcohol, polyacrylate, polyvinylpyrrolidone, carboxymethylcellulose, methylcellulose, calcium stearate, and ethylene bisstearamide, as well as calcium pyrophosphate, calcium phosphate, calcium carbonate, and carbonate. Inorganic compounds made of fine powder that are poorly soluble in water, such as magnesium, magnesium phosphate, magnesium pyrophosphate, and magnesium oxide, are used. In this invention, when using an inorganic compound as a dispersant, it is preferable to use a surfactant such as sodium dodecylbenzenesulfonate. These dispersants are generally
It is used by adding 0.01 to 5% by weight. The active hydroxy group in the hydroxy compound of this invention means a hydroxy group that can react with the maleic anhydride molecules of the styrene-maleic anhydride copolymer resin at elevated temperatures. It is particularly preferred that the number of active hydroxy groups is two. Examples of the compound having two active hydroxy groups include aliphatic dioxy compounds, aromatic dioxy compounds, aliphatic dioxy compounds containing an aromatic ring, and aliphatic diethanolamide.
A more specific example of this is as follows. (i) Aliphatic dioxy compound: Here, the aliphatic residue includes various structures such as structures containing saturated or unsaturated linear, branched, cyclic, or alicyclic residues. Specific examples include the following compounds. (a) In the general formula HO−(CH ₂ −) _o OH, n is 2 to
10 compounds, e.g. ethylene glycol,
Propylene glycol, etc. (b) In the general formula H〓O-R〓 _o OH, n is 2~
Compounds in which R in 6 is an alkylene group, such as diethylene glycol, dipropylene glycol, tetraethylene glycol, tetrapropylene glycol, and the like. (c) In addition to the above, compounds represented by the following formulas can also be used. (ii) Aromatic dioxy compounds: (a) Polyhydric phenols: hydroquinone, resorcinol, catechol and their lower alkyl- or chloro-substituted derivatives, pyrogallol-
Compounds having two hydroxy groups in an aromatic nucleus or a substituted aromatic nucleus, such as 1-methyl ether and pyrogallol-2-methyl ether, can be mentioned. (b) A compound represented by the following general formula: In the formula, -R- is 〓CH ₂ , 〓CHCH ₃ , 〓CH(CH ₂ ) ₂ CH ₃ ,

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【formula】

【formula】

【formula】

【formula】

[Formula] -O-, -S-, -SO-,

[Formula] etc., where X, Y, X', and Y' are the same or different and mean a hydrogen atom, a halogen atom, a lower alkyl group, etc. Particularly preferred among this group of compounds is bisphenol A [2,2-bis(4'-hydroxyphenyl)]
propane]. (iii) Aliphatic dioxy compounds containing aromatic rings: Compounds that fall into this category include, for example, compounds with the general formula HO-(CH ₂ -) _o R'-(CH ₂ -) _o OH where n is 1 or 2; , R′ is a group as follows:

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

【formula】

[Formula] Compounds may be mentioned. (iv) Fatty acid diethanolamide: Here, the aliphatic residue of the fatty acid includes various structures such as linear, branched, cyclic, or structures containing alicyclic residues. In this case, the fatty acid may also be a mixed fatty acid of various fatty acids having different numbers of carbon atoms. A preferred specific example is diethanolamide of coconut oil fatty acid. Examples of compounds having three or more active hydroxy groups include glycerin, pentaerythritol, and the like. The above hydroxy compound is added in an amount of 2.5 mol % or more based on the total amount of maleic anhydride molecules in the styrene-maleic anhydride copolymer resin. Generally, it may be added in amounts up to 150 mol%. If the amount added is less than 2.5 mol%, a good foamed molded article cannot be obtained unless the pre-expanded particles from the obtained expandable particles are overfilled, and the object of the invention cannot be achieved. Also, the use of a large excess of hydroxy compound relative to the content of acid anhydride groups would not make sense from an economic or technical point of view. The reaction between the styrene-maleic anhydride copolymer resin particles and the hydroxy compound is carried out at a temperature of 80°C to 150°C, preferably 90°C to 110°C (depending on the reaction temperature and the size of the copolymer particles). However, it is carried out by heating and stirring for 4 to 60 hours. It is believed that the hydroxy group of the hydroxy compound attacks the acid anhydride group in the molecular chain of the styrene-maleic anhydride copolymer to open the ring and generate a half-ester bond. At this time, it is thought that the two hydroxy groups of the hydroxy compound react with the acid anhydride groups of the separate copolymers to form a half-ester bond and also form a type of crosslinked structure.
It is believed that this increases the secondary foaming power when pre-expanded particles are impregnated with a foaming agent, and that various effects such as reducing the thermal shrinkage rate of the resulting foam molded product are expected to occur. It will be done. The particles of styrene-maleic anhydride copolymer resin may be impregnated with a blowing agent before the above reaction,
It may also be carried out during or after the reaction. However, it is most preferred in industrial practice to add the hydroxy compound and the volatile blowing agent to the same reaction system and to carry out the esterification reaction and blowing agent impregnation in the same process. Volatile blowing agents in this invention include propane, n-butane, i-butane, n-pentane,
Aliphatic hydrocarbons such as i-pentane and n-hexane, cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane, halogenated hydrocarbons such as methyl chloride, ethyl chloride, dichlorodifluoromethane, chlorodifluoromethane, and trichlorofluoromethane. can be mentioned. Among these blowing agents, preference is given to using propane or n-butane and mixtures thereof. These blowing agents are generally used in an amount of 3 to 40% by weight based on the copolymer resin particles. In this invention, when adding the above-mentioned blowing agent, it is preferable to include a solvent that dissolves the styrene-maleic anhydride copolymer resin particles. This solvent is preferably stirred and dispersed in an aqueous suspension in advance so that it is sufficiently impregnated into the styrene-maleic anhydride copolymer resin particles. Such solvents include aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, esters such as methyl acetate and ethyl acetate, halogenated hydrocarbons such as dichloroethane, trichloroethane, tetrachloroethane, trichloroethylene and tetrachloroethylene, cyclohexane and cycloheptane. cyclic compounds such as n-hexane,
Hydrocarbons such as n-heptane are used. The base resin of the expandable particles of the present invention contains fillers (for example, talc), plasticizers (for example, dioctyl phthalate), flame retardants (for example, tris(2,3-dibromopropyl) phosphate), and lubricants (for example, chlorinated paraffin, low density polyethylene), colorants (e.g. orthophenylphenol, biphenyl), ultraviolet absorbers (e.g. substituted hydroxyphenylbenzotriazoles), antioxidants (e.g. β, β'-thiopropionate), etc. Various additives may be contained. By subjecting the expandable styrene-maleic anhydride copolymer resin particles of the present invention to a foam fusion molding method, a foamed molded article with excellent heat resistance and low specific gravity can be obtained. A foamed molded article can be obtained using the particles by a conventional method, for example, as follows. a Manufacturing process of pre-expanded particles The expandable particles of this invention are charged into a normal batch-type or continuous-type pre-expander used for pre-expanding expandable polystyrene particles, and the original pressure is
Supply 0.2-0.3Kg/ ^cm2 of water vapor. The bulk specific gravity of the pre-expanded particles is adjusted by the water vapor supply time. The obtained pre-expanded particles are aged in a Saran mesh silo for about 12 hours. b Manufacturing process of foamed molded product To obtain a foamed molded product from the pre-expanded particles, an expandable polystyrene molding machine is used as is. However, since the expandable styrene-maleic anhydride copolymer resin particles of the present invention have extremely good adhesion to metals when heated, it is necessary to perform a treatment such as Teflon coating on the mold surface that comes into contact with the pre-expanded particles. . This mold has a mold surface treated with Teflon coating, etc.
Generally, the cavity is filled with the same volume of pre-expanded particles. In addition, in the case of an automatic molding machine, cracking of 1 to 3 mm is used to make it easier to fill the pre-expanded particles, so the excess amount of the cracked particles is filled, and then the mold is closed.
Although it varies depending on the size and thickness of the foam molded product to be obtained, generally 0.5 to 2.0 kg/cm ² of water vapor is used.
Inject into the mold for 30-180 seconds. Next, after cooling the mold with water, the mold is opened and the obtained foamed molded product is taken out. As described above, a foamed molded article is obtained using the expandable styrene-maleic anhydride copolymer resin particles of the present invention. Note that the expandable styrene used in this invention
Maleic anhydride copolymer resin particles have good adhesion to metals, and when the polymer particles are foam-molded and at the same time a metal plate is bonded and laminated to the foamed product, the adhesion is extremely strong, resulting in an integrated laminate. is obtained.
These laminates, in which metal plates are laminated on one or both sides of the molded body, are extremely useful as heat insulating or cushioning materials for refrigerators, buildings, etc. This laminate is created as follows. A plate of aluminum, galvanized iron, nickel, iron, copper, or the like is placed in a mold in advance and adsorbed to the surface of the mold by suction, and then filled with the pre-expanded particles. Of course, it is also possible to insert the plate described above into the mold after filling it with pre-expandable particles. Since the pre-expanded particles of the expandable styrene-maleic anhydride copolymer resin particles of this invention have excellent secondary foaming power, it is generally sufficient to fill them to the same volume as the mold cavity. However, in the case of automatic molding machines, generally 1 to 3 mm is used when filling the pre-expandable particles.
Since cracking is employed, an excess of pre-expanded particles is filled by the amount of cracking.
In addition, when pre-expanded particles are automatically filled with air, they are uniformly filled into the mold, but by filling them by dropping them from a silo, a block-shaped foam molded product with a size of, for example, 182 x 91 x 40 cm is obtained. When trying to fill the cavity, it is not filled uniformly, so the cavity capacity is
Filled with pre-expanded particles within 110%. In addition, an automatic molding machine consisting of a moving mold and a fixed mold is used.
When attempting to obtain a plate-shaped foam molded product of 182 x 91 x 5 cm, with a maximum cracking of about 3 mm in the movable mold and the fixed mold, fill the cavity with 106% of the capacity of the pre-foamed particles. Filling the foam to more than 110% capacity is meaningless since it only increases the specific gravity of the foam molded product. After filling the mold with pre-expanded particles as described above, the mold is closed and water vapor is generally 0.5 to 2.0 Kg/ ^cm2 , although it varies depending on the size and thickness of the laminate and the type and thickness of the metal plate. 30～
Inject into the mold for 180 seconds. Next, the mold is cooled with water and the foam molded product is taken out. Next, the present invention will be explained with reference to examples. Example 1 Add 2800 ml of water to an autoclave with a content of 5
g, metathesis method 4.8 g of magnesium pyrophosphate and 0.2 g of sodium dodecylbenzenesulfonate were added, and then pellet-shaped styrene-maleic anhydride copolymer resin with a length of 3 cm and a diameter of 1.2 mm [maleic anhydride as a copolymerization component] was added. Content is 8.0% by weight,
Average degree of polymerization: 1200, Dilarc 232
(Dylark 232) (trade name, manufactured by Alco Polymers, USA) 1600 g of particles were added and suspended, and then 64 g of diethylene glycol and 64 g of toluene were added. Then, butane is added as a blowing agent while stirring in a closed state.
160g was press-fitted. The temperature was then raised to 100°C and maintained at this temperature for 18 hours. Thereafter, the mixture was cooled to 30° C. and the expandable particles impregnated with the foaming agent were taken out. After washing, dehydrating and drying the particles, they were placed in a sealed container and kept at a temperature of 15°C for 72 hours. When these particles were pre-foamed by heating with steam at 98°C for 20 minutes, pre-foamed particles having a bulk specific gravity of 0.013 were obtained. The pre-expanded particles were adjusted to have a bulk specific gravity of 0.022,
A mold with a depth of 25 mm and an internal volume of 3000 cm ³ is filled with 3000 cm ³ of pre-expanded particles to produce 1.0 Kg/cm ³ (gauge pressure).
Foam molded by heating with water vapor for 40 seconds
A good foam molded product having a specific gravity of 0.022 was obtained. The foam molded product obtained here was annealed at 50℃ for 24 hours, and then placed in a constant temperature oven with air circulation at 90℃.
When left for 12 days, it showed a shrinkage of 1.3%. Furthermore, when this foamed molded product was subjected to infrared analysis, absorption peaks based on ester bonds were observed. In addition, when the expandable particles were immersed in toluene, insoluble matter swelled in a nearly spherical shape (approximately 15 w/w% of the expandable particles).
remained. This insoluble material is considered to be a product of crosslinking. On the other hand, the average degree of polymerization of the toluene-soluble portion was 1500. Example 2 Particles impregnated with a blowing agent were obtained under the same conditions as in Example 1 except that various hydroxy compounds were added instead of diethylene glycol, and the particles were similarly made into pre-expanded particles, which were then filled into a mold and molded. The bulk specific gravity of the pre-expanded particles, the specific gravity of the obtained foamed molded article, and its thermal dimensional shrinkage rate (one direction) were measured. The results are shown in Table 1.

【table】

[Table] Example 3 An autoclave with an internal volume of 5 and a length of 3
mm, 1.2 mm in diameter, pellet-shaped styrene-maleic anhydride copolymer particles with a maleic anhydride content of 8% [average degree of polymerization: 1200, product name Dylark 232] , manufactured by Alco Polymers, USA] 1600g, water
2800g double decomposition method magnesium pyrophosphate 4.8g,
Sodium dodecylbenzenesulfonate 0.2g,
Add 64g of toluene and 64g of diethylene glycol, raise the temperature to 100℃ while stirring, and at this temperature
It was maintained for 18 hours. Thereafter, it was cooled to 30°C (some of the particles were taken out and immersed in toluene for 24 hours, and spherical, swollen insoluble matter remained), and then 160 g of butane was injected under pressure in a sealed state. Next, the temperature was raised to 100℃, and at this temperature 8
Time was maintained. Thereafter, it was cooled to 30°C and the foamable particles impregnated with the foaming agent were taken out. The expandable particles obtained here exhibited the same expandability and moldability as the expandable particles obtained in Example 1. Example 4 In place of the styrene-maleic acid copolymer in Example 1, a styrene-maleic acid copolymer (Dylark 232B) (A) containing 5 w/w% maleic anhydride component and an average degree of polymerization of 1400 and anhydrous Each sample was treated in the same manner as in Example 1 using a styrene-maleic acid copolymer (Dylarc 332) (B) having a maleic acid component of 14 w/w % and an average degree of polymerization of 740. The performance of the obtained pre-expanded particles and foamed molded article is shown in the following table.

[Table] Comparative Example 1 Expandable particles were obtained in the same manner as in Example 1 except that 80 g of ethanol was used instead of 64 g of diethylene glycol. These expandable particles are heated with water vapor at 98℃.
After foaming for 20 minutes, pre-expanded particles having a bulk specific gravity of 0.012 were obtained. In addition, this pre-expanded particle
When the bulk specific gravity was adjusted to 0.022 and filled into the same mold as in Example 1, only the molded products with a specific gravity of 0.027 or more showed good moldability, and the molded products with a specific gravity of 0.025 showed no shrinkage in appearance. It was sufficient.
The thermal dimensional shrinkage rate of this molded article having a specific gravity of 0.027 was 1.7%. Comparative Example 2 Expandable particles were produced in the same manner as in Example 1 except that diethylene glycol was not added. Using the obtained expandable particles, a foamed molded article was created in the same manner as in Example 1. Specific gravity is 0.022
To obtain a molded product with a low specific gravity of g/ ^cm2 , the mold volume must be 50
% excess pre-expanded particles had to be filled. Example 5 A fixed mold is composed of a movable mold, and when the fixed mold and the movable mold are closed, the internal dimensions of the mold cavity are
Using an automatic molding machine with a size of 182 x 91 x 5 cm (inner volume 82810 cm ³ ) and with Teflon coating on the mold surface that comes into contact with the pre-expanded particles, the pre-expanded particles were moved with a fixed mold to facilitate air filling. The pre-expanded particles obtained by the same method as in Example 1 are filled by an air filling method into a mold having a clearance of 2 mm for air removal between the mold and the mold. The filling amount at this time is 104% of the capacity of the mold cavity when the fixed mold and movable mold are closed.
After filling, the movable mold is operated and brought into close contact with the fixed mold to close the mold. Next, 0.2Kg/ ^cm2 of water vapor was added for 20 minutes.
It is preheated by injecting it for seconds, and then it is further heated for 40 seconds with 1.0 Kg/cm ² of steam. After the main heating is completed, the steam is discharged and the product is cooled with water for 40 seconds. Then drain the cooling water and leave to cool for 90 seconds. After cooling, the movable mold is moved to open the mold and the obtained molded body is taken out.
The specific gravity of the obtained molded product after annealing at 50° C. for 24 hours was about 0.023 g/cm ³ , and the appearance was the same as that of the foamed molded product obtained in Example 1. Example 6 Molding Using the same automatic molding machine and pre-expanded particles as in Example 1, an aluminum plate having a size of approximately 182 x 91 x 0.03 cm was placed on the movable mold surface of the automatic molding machine in advance by vacuum action. Let it be adsorbed by
The pre-expanded particles were filled, molded and cooled in the same manner as in Molding Example 1. The filling capacity at this time was 104.02% of the mold cavity capacity.
The aluminum plate was firmly adhered to the obtained expandable particles. The peel strength of this laminate in which the aluminum plate was adhesively laminated on one side was measured by the method of ASTM903-49, and it was found to be 0.7 kg/25 cm, and it was peeled off with the broken foam adhering to the metal plate surface. Similarly, when polystyrene was used instead of the foamable styrene-maleic acid copolymer resin of the present invention, the aluminum plate and polystyrene did not adhere at all.

Claims (1)

[Claims] 1. A styrene-maleic anhydride copolymer resin is reacted with a hydroxy compound having 2 to 4 active hydroxy groups in an amount of 2.5 to 150 mol% based on the maleic anhydride molecules, and the resin is volatilized. The foamed particles are impregnated with a foaming agent to obtain expandable particles, and then the expandable particles are made into pre-expanded particles, and the obtained pre-expanded particles are filled into a mold in an amount equal to or 10% in excess of the capacity of the cavity. 1. A method for producing a foamed molded article, the method comprising: molding the foamed article to obtain a foamed article having a low specific gravity and good thermal stability. 2. The method according to claim 1, wherein the molding die is made of metal, and the surface of the die that comes into contact with the pre-expanded particles is treated with a coating agent such as fluororesin. 3. A plate of metal such as aluminum, iron, stainless steel, copper, nickel or galvanized iron is placed on the inner surface of a metal mold and then filled with pre-expanded particles. Method described. 4. The method according to any one of claims 1 to 3, wherein the styrene-maleic anhydride copolymer resin contains 2 to 25% by weight of a maleic anhydride component and has an average degree of polymerization of 500 to 4,000.