JPH0249333B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to expandable synthetic resin particles, and more particularly to expandable synthetic resin particles having heat resistance. In general, styrene foam moldings are well known as synthetic resin foams. The processing process is also well known, and the outline is as follows. Expandable polystyrene particles (original particles) obtained by adding easily volatile components such as butane and pentane as a blowing agent to polystyrene beads obtained by suspension polymerization etc. are foamed to a predetermined ratio using steam etc. to prepare them. Eggplant with foam particles. After that, the pre-expanded particles are left in a silo for several tens of hours to adjust the volatile components and internal pressure of the particles (generally called a curing process), and then the pre-expanded particles are filled into a mold and steamed. The beads are heated to fuse and fuse together to form a molded body. However, since the styrene foam molded product obtained in this way has styrene as the monomer constituting the polymer, it is used in fields where it is used at relatively high temperatures (approximately 80°C or higher), such as hot water and hot water lines. Not commonly used as a heat insulator. Therefore, several types of expandable resin particles have recently been developed and reported for use in fields where heat resistance is required. For example, tertiary butyl styrene 20
~100% by weight of other polymerizable monomers, and the polymer particles contain 3~15% by weight of a readily volatile blowing agent (Japanese Patent Application Laid-open No. 56-92931), and emulsion polymerization method. α-alkylstyrene 15-55% by weight
A method of obtaining heat-resistant foamable resin particles by obtaining a copolymer with other polymerizable monomers and incorporating an easily volatile blowing agent into the polymer particles (Japanese Patent Application Laid-Open No. 1989-1999)
65735), and a method using a copolymer of maleic anhydride and styrene has also been reported. If a foam molded product intended for use at relatively high temperatures (approximately 80°C or higher) is called a heat-resistant foam molded product, the performance required of this product is to maintain the performance for a long time at the operating temperature. The dimensions of the molded body are stable, the molded body does not bend or warp, and the particles near the surface of the molded body do not foam. Therefore, in order to further improve the heat resistance of the obtained heat-resistant foamed molded product, it is necessary to further reduce the amount of foaming agent remaining in the molded product. Therefore, the molded product is
A method of reducing the amount of blowing agent by drying at a temperature 40°C lower (conditioning) is known. However, in this method, a high conditioning temperature requires a large amount of drying energy, and a low temperature requires a long time to reduce the blowing agent, resulting in a decrease in productivity. Therefore, by using expandable particles containing a small amount of blowing agent from the beginning, it is expected that a molded article with good heat resistance can be obtained. However, in this case, it is difficult to obtain a molded product with a high magnification, leading to an increase in costs, and if you try to mold with a high magnification, the particles filled in the mold will shrink during steam heating in the mold, making it difficult to mold properly. This problem arises. As a result of intensive research in view of such problems, the present inventors have found that a small amount, for example, per 100 parts of resin (all parts by weight hereinafter), is applied to the surface of the heat-resistant foamable polymer particles used.
Pre-foaming is carried out by adding 0.01 to 1 part, preferably 0.03 to 0.5 parts of a lubricant, and the heat resistance of the molded product obtained by using such particles is greatly improved compared to one without the use of a lubricant. I found out what to do. The heat-resistant foamable polymer particles referred to herein may be those whose base resin has a softening point higher than the softening point of polystyrene and which can be used as beads for foaming. Specifically, it is desirable to have a Vicatto softening point of 105°C or higher, preferably 110°C or higher, according to JIS method K-7206 (1 kg load method). That is, the base resin is made of a polymer, copolymer, or a mixture thereof of a monomer (hereinafter referred to as a heat-resistant monomer) whose homopolymer softening point is higher than that of polystyrene. As heat-resistant monomers, α-methylstyrene, α
-ethylstyrene, α-n-propylstyrene,
α-alkylstyrene such as α-iso-propylstyrene, 2- or 4-alkylstyrene such as 2-methylstyrene, 4-methylstyrene, 4-tert-butylstyrene, or 2,4- or 2,5-dimethylstyrene Dialkyl styrenes such as 2 or 4
Examples include halogenated styrenes such as -hydroxyalkylstyrene, 2- or 4-halogenated styrene, and 2,4- or 2,6-dihalogenated styrene, maleic anhydride, and the like. or

A base resin containing a bonding unit of the formula: (R, R' are an alkyl group or a phenyl group) is also effective. In other words, polymers consisting of one or a mixture of heat-resistant monomers, copolymers of these heat-resistant monomers with other monomers, or blends of these polymers with other polymers with relatively low softening points are the main ones. Used as a base resin in the invention. The content ratio of the heat-resistant monomer is preferably 20 to 100% by weight, but when maleic anhydride is contained as the heat-resistant monomer, the content ratio is 5 to 30% by weight, or

When using the formula (R, R' are as described above) as a heat-resistant bonding unit, it is preferable to contain it in an amount of 10 to 80% by weight from the viewpoint of processability. Next, the lubricant used may be any lubricant as long as it has the ability to interact with the polymer particles and erode the particle surfaces during the pre-foaming step. However, when selecting a lubricant, it is preferable to avoid a lubricant species or an amount used that causes a blocking phenomenon, which is a phenomenon in which particles coalesce during pre-foaming.
Examples of good lubricants having a melting point of 100°C or less include higher fatty acid esters such as diglycerides or triglycerides of higher fatty acids, sorbitan triesters of higher fatty acids, higher fatty acid diesters of glycols, and higher fatty acid esters of higher monoalcohols. In addition, hydrogenated animal oils such as hydrogenated beef tallow oil, hydrogenated vegetable oils such as hydrogenated soybean oil, hydrogenated rapeseed oil, and hydrogenated castor oil, as well as liquid natural oils such as olive oil, soybean oil,
Rapeseed oil is also good. Sulfur-containing esters such as distearyl-3,3' thiodipropionate are also effective. The number of lubricant added is 0.01 part (resin
If the amount is less than 100 parts, a sufficient effect of improving heat resistance cannot be obtained, and if it exceeds 1 part, the heat resistance of the molded product may deteriorate, mold fusion may deteriorate, or the moisture content in the molded product may decrease. Problems such as increase in the number of people are likely to occur. Therefore, the amount of lubricant is preferably 0.01 to 1 part. In particular, hydrogenated animal oils and hydrogenated vegetable oils are particularly suitable as lubricants that are effective in improving heat resistance even in small amounts and are well-balanced in terms of blocking properties and other aspects. In addition, a foaming aid is added to the foamable particles used.
It is preferable to contain the lubricant in an amount of 0.01 to 5 parts in order to achieve a sufficient effect with a relatively small amount of lubricant. The foaming aid mentioned here is used to plasticize the resin particles to facilitate foaming, and includes, for example, residual monomer, toluene, ethylbenzene, cyclohexane, hexane, heptane, octane, and the like. As mentioned above, just by adding a small amount of lubricant to the surface of heat-resistant expandable particles, the heat resistance of the molded product can be greatly improved, and even if conditioning is used, it is practically impossible to reach that temperature. The temperature is low and requires only a short time. If one attempts to obtain a product with good heat resistance without using a lubricant, it will be necessary to further increase the heat resistance of the base resin, which will make the pre-foaming process and molding process difficult. The above-mentioned problems can be avoided by using heat-resistant expandable particles and a lubricant in combination according to the present invention. This will be explained below using examples. Example 1 In an autoclave equipped with a stirrer, 110 parts by weight of water, 0.15 parts by weight of tertiary calcium phosphate, 0.01 parts by weight of sodium α-olefin sulfonate, and sodium chloride.
Then, under stirring, add 0.3 parts by weight of benzoyl peroxide and 1,1-bis(tert-butylperoxy)3,3,5-trimethylcyclohexane.
A monomer mixture of 35 parts by weight of 2-methylstyrene and 65 parts by weight of styrene in which 0.1 part by weight and 1.0 part by weight of toluene were dissolved was introduced into the system to form a suspended state. Next, the system was heated to 95°C and polymerized for 6 hours, after which 10 parts by weight of butane was added as a blowing agent, and the temperature was then raised to 110°C.
After keeping at 110℃ for 8 hours, cool to 40℃ and dehydrate and dry.
Sieving was performed to obtain a sample (sample A) with a particle size of 710 to 1100 μm. Further, this base resin was dried at 120°C for 3 days and the Vikato softening point was measured according to JIS-K-7206 method, and it was found to be 115°C. Next, various lubricants were added, and foaming magnifications of 30 and 40 times were obtained using a foaming machine. After being left at room temperature for one day, molding was performed to obtain a good molded product. As a heat resistance test, the molded product was continuously heated at 95°C, 100°C, and 105°C for 168 hours using a soaking dryer, and the maximum dimension (length) change rate of the molded product before and after heating was measured. The results are shown in Table 1. The amount of lubricant added was 0.05 part and 0.10 part. In addition to the lubricant, 0.03 part of zinc stearate was added as an antiblocking agent.

[Table] (Note) Sample No. ~ had a regular shape after the test, but Comparative Example No. had a concave shape in the center.
Further, the amount of blocking during preliminary foaming was measured and was as shown in Table 2 below.

【table】

[Table] The amount of blocking is expressed as the weight percent of blocking particles (separated through a sieve with a mesh size of 4.76 mm) based on the amount of particles used. However, the amount of volatile components of the particles used (180℃
x1 hour drying loss) was 8.2%. Example 2 In the recipe for obtaining sample A shown in Example 1, 2
Sample B was obtained in the same manner except that -methylstyrene was replaced with tert-butyl-styrene. This sample was subjected to the same heat resistance evaluation as in Example 1, and the results shown in Table 3 below were obtained. Note that the Vicat softening point of Sample D was 118°C.

[Table] Example 3 Sample C was obtained in the same manner as in Example 1 except that in the recipe for obtaining Sample A shown in Example 1, 1.0 parts by weight of toluene was replaced with no toluene and 10 parts by weight of butane was changed to 5.0 parts. A heat resistance test was conducted at a molding magnification of 5 times and 10 times, and the results shown in Table 4 below were obtained.

[Table] Example 4 2-
Where a mixed monomer of 35 parts by weight of methylstyrene and 65 parts by weight of styrene is used, 100 parts by weight of 4-
Sample D was obtained in the same manner except that methylstyrene was used. Example 1 for this sample
A heat resistance evaluation similar to that carried out was conducted, and the results shown in Table 5 below were obtained. Note that the Vicat softening point of Sample D was 113°C.

[Table] Example 5 Stirrer, reflux pipe, nitrogen supply line, thermometer,
250 parts water, 30 parts sodium laurate, 0.0025 parts ferrous sulfate, 0.01 parts in a reactor equipped with a metering pump.
Add 1 part EDTA and 0.4 parts sodium formaldehyde sulfoxylate and heat to 60°C in a nitrogen stream. This system contains 30 parts of α-methylstyrene, 70 parts of styrene, and 0.3 parts of cumene hydroperoxide.
1 part, and 0.1 part of tert-dodecyl mercaptan as a chain transfer agent was continuously added over 6 hours. After adding
Postpolymerization is carried out for a further 1 hour at 60°C. The obtained latex is coagulated with 0.25 parts of magnesium chloride and then heat-treated to form a slurry. Thereafter, dehydration, washing and drying are performed to obtain a powdery copolymer. The powder thus obtained was blended with 0.1 part of ethylene bis stearylamide (EBS) to obtain micro pellets. Put 100 parts of the pellets into an autoclave equipped with a stirrer, add 110 parts of water and 0.5 parts of calcium phosphate.
parts, α-olefin sulfonic acid soda 0.026 parts,
Add 4.0 parts of Glauber's salt, heat to 90℃, and add toluene.
Add 1.4 parts and leave for 2 hours. Thereafter, 9.0 parts of butane as a blowing agent was introduced under pressure, and the temperature was raised to 110°C. After raising the temperature, the pellets were left to stand for 6 hours to allow butane to impregnate into the pellets. The beads thus obtained were spherical expandable polymer particles with a diameter of about 1.3 mm (referred to as sample D). Tests similar to those in Example 1 were conducted by externally adding several types of lubricants to D, and the results shown in Table 6 below were obtained. The Vicat softening point of Sample D was 119°C.

【table】

[Table] Example 6 PPO [(poly2,6-dimethylphenylene-1,
4,-oxide) (degree of polymerization 200)] 25 parts, polystyrene resin (Styron-666 manufactured by Asahi Dow Co., Ltd.) 75 parts,
40 m/m of 0.1 part of ethylene bis stearylamide
Diameter 1mm length 1-2mm with vent type extruder
Put 100 parts of the pellets into an autoclave equipped with a stirrer, add 110 parts of water, 0.3 parts of tribasic calcium phosphate, and 0.01 part of sodium α-olefin sulfonate, heat to 90°C, and then add 1.5 parts of toluene. Leave it for 2 hours. Thereafter, 90 parts of butane was added as a blowing agent and the temperature was raised to 110°C. After raising the temperature, the pellets were left to stand for 6 hours to allow butane to impregnate into the pellets. The beads thus obtained were perfectly spherical with a diameter of about 1.3 mm. The obtained beads were dehydrated and dried, and tests similar to those in Example 1 were conducted by adding 0.05 and 0.10 parts of several types of lubricants to 100 parts of the resin, and the results shown in Table 7 below were obtained.

[Table] For No. ~, 0.05 part of zinc stearate was added as an antiblocking agent. Note that samples No. ~ had a regular shape after the test, but sample No. had a concave shape in the center. The base resin had a value of 121° C. according to the JIS-K-7206 Vicatto softening point measurement method. Example 7 PPO [(poly2,6-dimethylphenylene-1,
4-oxide) (degree of polymerization 200)] 20 parts, ethylene bisstearylamide 0.06 part, toluene 1.5 parts,
A system in which 0.3 parts of benzoyl peroxide and 0.1 parts of 1,1-bis(terbutylperoxy)3,3,5-trimethylcyclohexane were dissolved in 80 parts of styrene monomer was mixed with 110 parts of water, 0.20 parts of tribasic calcium phosphate,
The mixture was stirred and suspended in an aqueous medium containing 0.006 parts of sodium α-olefin sulfonate in an autoclave equipped with a stirrer. Next, the system was heated to 90°C and polymerized for 8 hours, after which 9 parts of butane was injected as a blowing agent and the temperature was raised to 110°C. 40℃ after 6 hours at 110℃
Cooled to 710~
A particle size of 1100μ was obtained. The same test as in Example 1 was carried out by adding 0.05 parts of several types of lubricants to 100 parts of the beads thus obtained, and the results shown in Table 8 below were obtained. In addition, JIS-K- of the base resin
The Vikat softening point value based on 7206 was 119°C.

[Table] Sample No. was subjected to a heat resistance test at 100°C and 105°C, and the shape was bent and the center was depressed.

Claims (1)

[Scope of Claims] 1. The base resin made of a polymer or copolymer has a Vikato softening point (JIS-K-7206, 1Kg load method) of 105
0.01 to 1% by weight of a lubricant with a melting point of 100°C or less on the surface of the foamable resin particles, which are made by containing 3 to 15% by weight of an easily volatile foaming agent and 0.01 to 5% by weight of a foaming aid in resin particles having a temperature of 100°C or higher. Heat-resistant foamable resin particles made by coating. 2 The base resin is mono- or dialkylstyrene,
20-100% by weight of mono- or dihalogenated styrene monomers or mixed monomers and other polymerizable monomers
80-0% by weight, or 5-30% by weight of maleic anhydride and 95-70% of other polymerizable monomers.
The resin particles according to claim 1, which are polymers or mixtures obtained by polymerizing % by weight. 3 Mono- or dialkyl styrene is α- or 2
- or 4-alkylstyrene, 2,4- or 2,
The resin particles according to claim 2, which are 5-dialkylstyrene. 4 The base resin contains 10 to 80% by weight of bonding units represented by the formula (where R and R' represent C ₁ to ₄ alkyl groups or phenyl groups) and 90 to 20% by weight of other bonding units. The resin particles according to claim 1, comprising: 5. The resin particles according to claim 2 or 4, wherein the other polymerizable monomer or bonding unit is styrene. 6. The resin particles according to claim 1, wherein the blowing aid is selected from residual monomers, toluene, ethylbenzene, cyclohexane, hexane, heptane, octane, or mixtures thereof. 7 The lubricant is a higher fatty acid ester, hydrogenated animal oil,
The resin particles according to claim 1, which are selected from hydrogenated vegetable oils or mixtures thereof. 8 Higher fatty acid esters are triglycerides, sorbitan triesters, glycol diesters, and higher monoalcohol esters of higher fatty acids, and hydrogenated animal oils and hydrogenated vegetable oils include hydrogenated tallow oil,
The resin particles according to claim 7, which are hydrogenated soybean oil or hydrogenated rapeseed oil. 9. The resin particles according to claim 7, wherein the lubricant is a hydrogenated vegetable oil or a hydrogenated animal oil.