JP2015151486A - Expandable resin particle, production process, pre-expanded particle, and expansion molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an expansion-formed body that has a flame retardant capability, is excellent in heat resistance, has a less residual styrenic monomer, and furthermore is excellent in surface nature.SOLUTION: Provided is: an expandable resin particle comprising a blowing agent, obtained by co-polymerizing monomers selected from styrene monomer 60 pts.wt. or more and 75 pts.wt. or less, acrylonitrile monomer 21 pts.wt. to 27 pts.wt. or less, and alpha methyl styrene monomer 3 pts.wt. or more and 15 pts.wt. or less, so as the sum to be 100 pts.wt.; and an expansion molded article obtained by pre-expanding and in-mold molding an expandable resin particle containing bromine-based flame-retardant agent by 1.5 pts.wt. or more and 3.0 pts.wt. or less per 100 pts.wt. of said expandable resin particle.

Description

  The present invention relates to an expandable resin particle, a production method, pre-expanded particles, and an expanded molded article that are excellent in flame retardancy and heat resistance and have a low content of volatile organic compounds.

  Expandable polystyrene resin particles are well known as expandable resin particles. Expandable polystyrene resin particles are generally widely used because they can be easily obtained by in-mold foam molding and are inexpensive. Expandable polystyrene resin particles are excellent in light weight and heat insulation performance, but due to the low heat resistance of polystyrene, comparison of heat insulation materials for piping, heat insulation materials for roofs, automotive materials, solar system heat insulation materials, water heater insulation materials, etc. There was a problem with dimensional stability during long-term use under high temperatures.

  In order to solve the above problems, Patent Documents 1 and 2 describe heat-resistant styrene resin particles obtained by copolymerizing alphamethylstyrene and styrene. Although these heat-resistant styrene resin particles are excellent in heat resistance and flame retardancy, copolymerization of alphamethylstyrene and styrene makes it difficult to reduce residual styrenic monomers due to polymerization problems, and it is necessary to carry out reactions at high temperatures. was there.

  Patent Documents 3, 4, and 5 introduce styrene / acrylonitrile / alphamethylstyrene heat resistant styrene resin particles. In this invention, the flame retardancy and heat resistance are excellent, and the residual styrene monomer is reduced, but a large amount of flame retardant is used to obtain flame retardancy. Was not enough.

JP 2012-77149 A Patent No. 5080226 JP 2007-246666 A JP 2003-335891 A JP 2001-181433 A

  Although the expandable resin particles described in the above publication are excellent in flame retardancy and heat resistance, it is desired to provide a foamed molded article having excellent heat resistance, a small amount of residual styrene monomer, and excellent surface properties. ing.

  As a result of intensive studies, the present inventors have completed the present invention. That is, the present invention is as follows.

  (1) A monomer selected from 60 parts by weight to 75 parts by weight of styrene monomer, 21 parts by weight to 27 parts by weight of acrylonitrile monomer, and 3 parts by weight to 15 parts by weight of alphamethylstyrene monomer. Are foamable resin particles that are copolymerized to a total of 100 parts by weight and containing a foaming agent, and 1.5 parts by weight or more of a brominated flame retardant with respect to 100 parts by weight of the foamable resin particles. The present invention relates to an expandable resin particle containing 0 part by weight or less.

  (2) A peroxide having a one-hour half-life temperature of 130 ° C. or more and 150 ° C. or less is contained in an amount of 0.3 to 1.5 parts by weight with respect to 100 parts by weight of the expandable resin particles. (1) It is related with the expandable resin particle of description.

  (3) Brominated flame retardant is 2,2-bis [4 '-(2' ', 3' '-dibromo-2' '-methylpropyloxy)-, 3', 5'-dibromophenyl] -propane The present invention relates to the expandable resin particles according to (1) or (2).

  (4) The expandable resin particle according to any one of (1) to (3), wherein the content of the styrene monomer is 300 ppm or less.

  (5) The expandable resin particles according to any one of (1) to (4), wherein the amount of alphamethylstyrene monomer is copolymerized in an amount of 4 to 7 parts by weight.

  (6) Any one of (1) to (5) is characterized in that a dimensional change rate at 95 ° C. and 168 hours of the molded body prefoamed and molded at a foaming ratio of 40 times is 0.5% or less. It relates to the expandable resin particles described.

  (7) The foamable resin particles according to any one of (1) to (6), wherein the molded article is pre-foamed at a foaming ratio of 40 times and has an oxygen index of 28 or more.

  (8) The foamable resin particle according to any one of (1) to (7), which does not contain a high-boiling plasticizer having a boiling point of 200 ° C. or higher.

  (9) The expandable resin particle according to any one of (1) to (8), wherein the polystyrene-equivalent weight average molecular weight is from 150,000 to 200,000.

  (10) After the first polymerization at 85 ° C. or higher and 94 ° C. or lower in the presence of 0.5 parts by weight or more of a chain transfer agent using a bifunctional polymerization initiator, 10 hours half-life temperature 90 ° C. or higher and 100 ° C. The following high temperature decomposition type polymerization initiator is used in an amount of 0.1 parts by weight or more and 0.5 parts by weight or less, and the second polymerization is performed at 100 ° C. or more and 105 ° C. or less (1) to (9) It relates to the manufacturing method of the expandable resin particle in any one of these.

  (11) The present invention relates to pre-expanded particles obtained by pre-expanding the expandable resin particles according to any one of (1) to (9).

  (12) The present invention relates to a foamed molded article obtained by molding the pre-foamed particles according to (11) in a mold.

  According to the present invention, it is possible to provide a foamed molded article having excellent flame retardancy even with a small amount of flame retardant, excellent heat resistance, little residual monomer, and excellent surface properties.

  The expandable resin particles of the present invention comprise 60 to 75 parts by weight of styrene monomer, 21 to 27 parts by weight of acrylonitrile monomer, and 3 to 15 parts by weight of alphamethylstyrene monomer. 1. Expandable resin particles copolymerized to a total of 100 parts by weight of the selected monomers and containing a foaming agent, wherein 1. 1 part of a brominated flame retardant is added to 100 parts by weight of the foamable resin particles. 5 to 3.0 parts by weight is contained.

  The styrene monomer is preferably 65 to 75 parts by weight, more preferably 70 to 73 parts by weight. When the styrene monomer component is large, heat resistance cannot be obtained, and when it is small, the moldability tends to be inferior.

  The acrylonitrile monomer is preferably 23 parts by weight or more and 25 parts by weight or less. When there are many acrylonitrile monomers, a moldability will deteriorate, and when too large, polymerization stability will deteriorate. If the amount of acrylonitrile is small, the heat resistance deteriorates and the residual styrene monomer tends to be difficult to reduce.

  The alpha methyl styrene monomer is preferably 4 to 10 parts by weight, more preferably 4 to 7 parts by weight. When the amount of alphamethylstyrene monomer is small, heat resistance cannot be obtained, and when it is large, flame retardancy deteriorates and residual styrene monomer tends to remain.

  The expandable resin particles of the present invention contain a brominated flame retardant in order to obtain flame retardancy. The brominated flame retardant is contained in an amount of 1.5 to 3.0 parts by weight, preferably 1.8 to 2.5 parts by weight. When there are few brominated flame retardants, sufficient flame retardancy cannot be obtained, and when there are many brominated flame retardants, a residual monomer will remain easily and a moldability will also deteriorate. Brominated flame retardants include 2,2-bis [4 '-(2' ', 3' '-dibromo-2' '-methylpropyloxy)-, 3', 5'-dibromophenyl] -propane, hexa Examples include bromocyclododecane, tetrabromocyclooctane, brominated polystyrene, and brominated butadiene-styrene block copolymer. Among them, 2,2-bis [4 '-(2' ', 3' '-dibromo-2' '-Methylpropyloxy)-, 3', 5'-dibromophenyl] -propane is preferred.

  A flame retardant aid may be used in combination with the flame retardant. Radical generators such as peroxides are used as flame retardant aids, such as dicumyl peroxide, t-butyl peroxybenzoate, 2,3-dimethyl-2,3-diphenylbutane, and 3,4-dialkyl-3. 1,4-diphenylhexane and the like. Among them, a peroxide having a one-hour half-life temperature of 130 ° C. or more and 150 ° C. or less is preferable in order to obtain a small flame retardant effect and good flame retardancy. Dicumyl peroxide is particularly preferred. The flame retardant aid is preferably used in an amount of 0.3 to 1.5 parts by weight based on 100 parts by weight of the expandable resin particles. When the amount of the flame retardant aid is small, the flame retardancy is deteriorated, and when the amount is large, the heat resistance tends to be deteriorated.

  Examples of the method for producing the expandable resin particles of the present invention include suspension polymerization in which polymerization is performed in an aqueous suspension.

  The “aqueous suspension” in the present invention refers to a state in which resin particles and monomer droplets are dispersed in water or an aqueous solution by using stirring or the like. The body may be dissolved, and a water-insoluble dispersant, initiator, crosslinking agent, bubble regulator, flame retardant, plasticizer, and the like may be dispersed together.

  The weight ratio of the resin and water is preferably 1.0 / 0.6 to 1.0 / 3.0 as the ratio of the styrene resin / water obtained.

  Examples of the dispersant that can be used for suspension polymerization include poorly water-soluble inorganic salts such as tricalcium phosphate, magnesium pyrophosphate, hydroxyapatite, and kaolin, and water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone. In the case of using a poorly water-soluble inorganic salt, it is effective to use an anionic surfactant such as α-olefin sulfonic acid soda and dodecylbenzene sulfonic acid soda together. These dispersants may be added during the polymerization as required.

  The amount of the dispersant used depends on the type, but the water-insoluble inorganic salt is 0.1 to 1.5 parts by weight with respect to 100 parts by weight of water, and 30 ppm for the anionic surfactant or water-soluble polymer. The amount is preferably 100 ppm or less.

  In the suspension polymerization of the present invention, it is preferable that after the first stage polymerization is performed and the main reaction is performed, the residual monomer is reduced by the second stage polymerization reaction at a higher temperature than the first stage.

  As the polymerization initiator used in the first stage polymerization, radical generating polymerization initiators generally used for the production of thermoplastic polymers can be used. Typical examples include benzoyl peroxide and lauroyl. Peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperpivalate, t-butylperoxyisopropyl carbonate, di-t-butylperoxyhexahydroterephthalate, 1,1-di (t- Organic peroxides such as butylperoxy) 3,3,5-trimethylcyclohexane and 1,1-di (t-butylperoxy) cyclohexane, and azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile Is mentioned. These polymerization initiators may be used alone or in combination of two or more. In particular, in the monomer composition of the present invention, using an initiator having a 10-hour half-life temperature of 85 ° C. or higher and 94 ° C. or lower, and performing the first stage polymerization at 85 ° C. or higher and 95 ° C. or lower controls the polymerization reaction. Among them, a bifunctional polymerization initiator is preferable because it is easy to adjust the polymerization rate and the molecular weight. In particular, it is preferable to use di-t-butylperoxyhexahydroterephthalate (10-hour half-life temperature 83 ° C.). The amount of the polymerization initiator used in the first stage polymerization is preferably 0.1 part by weight or more and 1.0 part by weight or less, and more preferably 0.2 part by weight or 0.5 part by weight. If the amount of the polymerization initiator is small, the polymerization may not proceed sufficiently. If it is too large, the polymerization reaction may proceed rapidly and it may be difficult to control the polymerization.

  As the polymerization initiator used in the second stage polymerization, those having a 10-hour half-life temperature of 90 ° C. or more and 100 ° C. or less are preferable, and 1,1-bis (t-amylperoxy) -3, 3, 5 -Trimethylcyclohexane (10-hour half-life temperature 92 ° C), 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane (10-hour half-life temperature 97 ° C), t-butylperoxy- 2-ethylhexyl monocarbonate (10-hour half-life temperature 99 ° C), t-amylperoxy-2-ethylhexyl monocarbonate (10-hour half-life temperature 98.5 ° C), and the like. This second stage polymerization may be carried out in the presence of a blowing agent in combination with the blowing agent impregnation step. The polymerization initiator used for the second stage polymerization is preferably 0.1 part by weight or more and 0.5 part by weight or less, more preferably 0.15 part by weight or more and 0.3 part by weight or less. When the amount of the polymerization initiator is small, the residual styrene monomer tends to remain, and when it is large, it is difficult to adjust the molecular weight.

  In the polymerization in the present invention, α-methylstyrene dimer generally used for polymerization of mercaptan chain transfer agents such as n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan and acrylonitrile-styrene resin. Etc. can be used as a polymerization regulator. When the amount used is 0.5 parts by weight or more, it is easy to adjust the polymerization rate and molecular weight, and among them, the use of α-methylstyrene dimer is preferable because the odor of the foam does not occur.

  In particular, the expandable resin particles of the present invention use a bifunctional polymerization initiator, and after the first polymerization at 85 ° C. or more and 94 ° C. or less in the presence of 0.5 parts by weight or more of the chain transfer agent, the time is reduced by 10 hours and a half. A high temperature decomposition type polymerization initiator having an initial temperature of 90 ° C. or higher and 100 ° C. or lower is used by 0.1 to 0.5 parts by weight, and the second polymerization is carried out at 100 ° C. or higher and 105 ° C. or lower. Is preferred.

  The molecular weight of the expandable resin particles of the present invention can be adjusted by combining the polymerization initiator and chain transfer agent with polymerization conditions. The weight average molecular weight is preferably 150,000 or more and 200,000 or less. If the weight average molecular weight is 150,000 or less, the strength and flame retardancy of the obtained foamed molded product tend to be low, and if it is 200,000 or more, the moldability tends to deteriorate.

  As the additive used in the present invention, a plasticizer, a bubble regulator or the like can be used depending on the purpose. Examples of the plasticizer include high-boiling plasticizers having a boiling point of 200 ° C. or higher. Examples include vegetable oils such as palm kernel oil, aliphatic esters such as dioctyl adipate and dibutyl sebacate, and organic hydrocarbons such as liquid paraffin and cyclohexane, but they are not used because they tend to deteriorate the heat resistance. It is preferable.

  Examples of the air conditioner include aliphatic bisamides such as methylene bis stearic acid amide and ethylene bis stearic acid amide, polyethylene wax, and the like.

  The expandable resin particles of the present invention preferably have a styrene monomer content of 300 ppm or less. When the content of the styrene monomer is 300 ppm or more, there is a possibility of causing sick house syndrome when used in a heat insulating material or an automobile interior material.

  The obtained expandable resin particles can be made into pre-expanded particles by a general pre-expand method. Specifically, it is placed in a container equipped with a stirrer and heated by a heat source such as water vapor to perform preliminary foaming up to a desired foaming ratio.

  Further, the pre-expanded particles can be molded by a general in-mold molding method to form a foam molded body. Specifically, it is filled in a mold that can be closed but cannot be sealed, and heat-sealed with water vapor to obtain a foamed molded article.

  The foamed molded article of the present invention is pre-foamed at a foaming ratio of 40 times, and has an oxygen index of 28 or more in order to exhibit sufficient flame retardancy when used as a heat insulating material or automobile interior material when molded. preferable.

  When the foamed molded product of the present invention is used as a heat insulating material, it is preferable that the heat resistance is small when it is used at 90 ° C. or more. Specifically, the molded product is prefoamed and molded at a foaming ratio of 40 times. The dimensional change rate at 95 ° C. and 168 hours of the body is preferably 0.5% or less.

  Examples and Comparative Examples are given below, but the present invention is not limited thereby. In addition, about the molecular weight of resin in an Example and a comparative example, the amount of residual styrene in resin, the amount of phenyl acetylene in a styrene monomer, and evaluation of a flame retardance, it measured with the following method. “Parts” and “%” are based on weight unless otherwise specified.

(Molecular weight measurement method)
0.02 g of expandable resin particles were dissolved in 20 cc of tetrahydrofuran, and GPC (HLC-8020 manufactured by Tosoh Corporation, column: TSKgel Super HZM-H, column temperature: 40 ° C., flow rate: 0.35 ml / 1 min.) It was measured. The weight average molecular weight was determined as a converted value of standard polystyrene.

(Measurement of residual styrene monomer)
0.25 g of expandable resin particles were dissolved in 20 cc of methylene chloride (internal standard cyclopentanol), and gas chromatography (GC-14B, manufactured by Shimadzu Corporation), column: 3 m, packing agent: PEG-20M 25%, column temperature: 110 ℃, carrier gas: helium), the amount of residual styrene monomer and the amount of residual alphamethylstyrene monomer contained in the expandable resin particles are quantified from the calibration curve, and the total value becomes the expandable resin particles. On the other hand, it was considered acceptable at 0.03% or less. Those below the lower limit of detection were denoted as ND.

(Production of pre-expanded particles)
The expandable resin particles were sieved to obtain expandable resin particles having a particle diameter of 0.5 to 1.4 mm.

  The foamed resin particles thus separated were pre-foamed to a bulk magnification of 40 times under the condition of a blowing vapor pressure of 0.09 to 0.10 MPa using a pressure type pre-foaming machine “Daikai Kogyo BHP”. This was left for 1 day to obtain pre-expanded particles having a bulk magnification of 40 times.

(Manufacture of foam moldings)
The obtained pre-expanded particles are blown into a mold using a molding machine “Daisen, KR-57” at a blown vapor pressure of 0.05 MPa, thereby forming a flat-plate foam having a thickness of 20 mm, a length of 400 mm and a width of 350 mm. A molded body was obtained.

(Surface properties of molded products)
The state of the surface of the foamed molded product was evaluated by visual observation. The larger the numerical value, the more beautiful the surface state with few gaps between particles, and 3 or more expressed with a perfect score of 5 was regarded as acceptable.
5: Gaps are not found 4: There are some gaps, but I don't really know 3: There are some gaps, but it is acceptable as a whole 2: Gaps are conspicuous 1: There are many gaps

(Oxygen index)
A foamed molded product having a molded product magnification of 40 times was dried at 60 ° C. for 12 hours. Then, the sample piece cut out to 10x10x200mm was measured based on JISK7201 (flammability test method by an oxygen index), and 28 or more was set as the pass.

(95 ° C dimensional shrinkage)
A foamed molded product having a molded product magnification of 40 was dried at 60 ° C. for 24 hours. Thereafter, the molded body was cut out to a length of 150, a width of 150, and a thickness of 20 (t) mm, and the initial dimension (A) was determined by measuring the length and width dimensions at three locations. Then, it was left to stand in a dryer at 95 ° C. for 168 hours, and after left to stand, the same measurement was performed to determine the dimension (B). The dimensional shrinkage rate was calculated by the following formula, and 0.5% or less was accepted.
Dimensional shrinkage (%) = ((A)-(B)) / (A) × 100

(Examples 1-11, Comparative Examples 1-9)
In a 6 L autoclave with a stirrer, 110 parts by weight of water, 0.105 part by weight of tricalcium phosphate, 0.0075 part by weight of sodium α-olein sulfonate, and a polymerization initiator, a chain transfer agent in the amounts shown in Table 1, difficulty A flame retardant, a flame retardant aid, and a plasticizer were charged and deoxidized with a vacuum pump to a gauge pressure of -0.06 MPa. Thereafter, stirring with a stirrer was started, and styrene, alphamethylstyrene, and acrylonitrile in amounts shown in Table 1 were charged, and stirring was performed for 30 minutes. Then, it heated up to 90 degreeC and implemented 1st superposition | polymerization by hold | maintaining at 90 degreeC for 5 hours and 30 minutes. Thereafter, 5 parts by weight of normal rich butane (normal / iso = 70/30) was charged, the temperature was raised to 102 ° C., impregnation with a blowing agent and second polymerization were performed for 8 hours. Thereafter, the foamed resin particles were taken out by cooling to 40 ° C., dehydration and drying. The molecular weight and residual styrene monomer were measured for the expandable resin particles. The results are shown in Table 1.

  The foamable resin particles obtained were prefoamed to obtain prefoamed particles, which were further molded in-mold to obtain a 40-fold foamed molded product.

  About the obtained foaming molding, surface property, an oxygen index, and 95 degreeC dimensional-change rate were evaluated. The results are shown in Table 1.

  Although the thing of Examples 1-11 which is the range of this invention passed the residual styrene-type monomer, the surface property of a molded object, an oxygen index, and 95 degreeC dimensional change rate, the thing of Comparative Examples 1-9 Is not acceptable because it deviates from the requirements of the present invention.

Claims (12)

A total of 100 monomers selected from 60 parts by weight to 75 parts by weight of styrene monomer, 21 parts by weight to 27 parts by weight of acrylonitrile monomer, and 3 parts by weight to 15 parts by weight of alphamethylstyrene monomer. Foamable resin particles that are copolymerized so as to be parts by weight and include a foaming agent, and containing 100 parts by weight of the foamable resin particles of 1.5 parts by weight or more and 3.0 parts by weight of a brominated flame retardant Expandable resin particles characterized by containing: 2. A peroxide having a one-hour half-life temperature of 130 ° C. or more and 150 ° C. or less is contained in an amount of 0.3 to 1.5 parts by weight with respect to 100 parts by weight of the expandable resin particles. The expandable resin particle as described. The brominated flame retardant is 2,2-bis [4 '-(2' ', 3' '-dibromo-2' '-methylpropyloxy)-, 3', 5'-dibromophenyl] -propane The expandable resin particle according to claim 1 or 2, characterized in that: The expandable resin particle according to any one of claims 1 to 3, wherein the content of the styrene monomer is 300 ppm or less. The expandable resin particle according to any one of claims 1 to 4, wherein the amount of alphamethylstyrene monomer is copolymerized by 4 to 7 parts by weight. The foamable resin according to any one of claims 1 to 5, wherein a dimensional change rate at 95 ° C and 168 hours of the molded body prefoamed and molded at a foaming ratio of 40 times is 0.5% or less. particle. The expandable resin particle according to any one of claims 1 to 6, wherein the foamed resin particle is pre-foamed at an expansion ratio of 40 times, and the molded article has an oxygen index of 28 or more. The expandable resin particle according to any one of claims 1 to 7, which does not contain a high-boiling plasticizer having a boiling point of 200 ° C or higher. The expandable resin particle according to any one of claims 1 to 8, wherein the polystyrene-equivalent weight average molecular weight is from 150,000 to 200,000. Using a bifunctional polymerization initiator, in the presence of 0.5 parts by weight or more of a chain transfer agent, after the first polymerization at 85 ° C. or more and 94 ° C. or less, a 10 hour half-life temperature of 90 ° C. or more and 100 ° C. or less The decomposition-type polymerization initiator is used in an amount of 0.1 part by weight or more and 0.5 part by weight or less, and the second polymerization is performed at 100 ° C. or more and 105 ° C. or less. Process for producing expandable resin particles. Pre-expanded particles obtained by pre-expanding the expandable resin particles according to any one of claims 1 to 9. A foam-molded article obtained by molding the pre-expanded particles according to claim 11 in a mold.