JP5820165B2 - Expandable thermoplastic resin particles - Google Patents

Description

  The present invention relates to expandable thermoplastic resin particles suitable for pre-expansion and in-mold molding at low temperatures.

  Expandable thermoplastic resin particles are a relatively useful material, and can be foam-molded with steam or the like without using a special method, so that a high buffering and heat insulation effect can be obtained. However, due to increasing interest in environmental issues in recent years, there has been a growing demand for energy saving. By reducing the temperature during pre-foaming and in-mold molding, a resin that can be foamed with a small amount of steam is required. It has been.

  The foamed molded article is manufactured by a method in which foamable thermoplastic resin particles are heated with steam or the like, pre-foamed to a desired bulk density, subjected to an aging step, filled in a molding die, and heated and foamed again. However, when the temperature at the time of foaming is lowered, there is a problem that not only pre-foaming to a desired bulk density but also the appearance of the obtained foamed molded product is remarkably deteriorated. In particular, when used in the food packaging material field or the medical field, it is desired that the monomer component remaining in the resin is less than 0.3%, but when the monomer component having plasticity decreases, There was a problem that foaming and moldability at low temperatures deteriorated.

In order to solve this problem, Patent Document 1 discloses a styrene and a monomer copolymerizable with styrene in the production of a foamable styrene resin using butanes as a foaming agent. A resin obtained by polymerization using 17% or less based on styrene, wherein the secondary transition temperature is 2 to 14 ° C. lower than that of the styrene resin, and the residual amount of monomer is 0.3% or less. Expandable styrenic resin particles having excellent foaming ability, which have been characterized, have been proposed.
In Patent Document 2, a styrene monomer and an acrylate monomer are copolymerized in an aqueous suspension, or a styrene monomer and an acrylate monomer are copolymerized in the presence of styrene polymer seed particles. A method for improving the foamability of styrenic polymer particles has been proposed.

  However, in the methods of Patent Documents 1 and 2, the foaming power is increased by lowering the secondary transition temperature, but the ratio of the acrylate ester particle surface to the central portion has not been studied, and molding at a low temperature is not performed. A satisfactory effect cannot be obtained with sex.

  Moreover, in patent document 3, at least 1 type of acrylic resin selected from the group which consists of a butyl acrylate polymer, a cetyl methacrylate polymer, and a butyl acrylate-methacrylic acid acrylate copolymer is used for a styrene-type monomer. There has been proposed a method for producing expandable styrene resin particles, wherein 0.1 to 6.0% by weight is dissolved in the resin component of the expandable styrene resin particles obtained. However, in Patent Document 3, in order to dissolve the acrylic resin in the styrene monomer in the initial stage, it becomes a styrene-acrylate block copolymer, but the styrene-acrylate block copolymer is thermally stable. In particular, the surface of the molded body is likely to melt when it is made highly foamed, and there is room for improvement in terms of the appearance of the molded body.

  Patent Document 4 proposes foamable thermoplastic resin particles obtained by impregnating a foaming agent into thermoplastic resin particles obtained by polymerizing a styrene monomer, diallyl phthalate, and acrylic acid ester or methacrylic acid ester. Yes. However, when a crosslinking agent such as diallyl phthalate is added to increase the molecular weight, there is room for improvement in that the moldability is deteriorated and the appearance of the surface of the molded article is impaired.

  In patent document 5, although it is a foaming method different from the present invention, styrene resin particles having a weight average molecular weight of 150,000 to 500,000 are used, and a fatty acid hydrocarbon having 5 or less carbon atoms having a side chain is obtained. Expandable styrene resin particles containing 3 to 10% by weight of a foaming agent as a main component, having a foaming start temperature of 50 to 70 ° C. and a maximum foaming temperature of 80 to 110 ° C., and a method for producing the same are proposed. However, it is copolymerized with butyl acrylate in order to improve foamability at low temperature, but because the amount of butyl acrylate used relative to the styrenic monomer is large, melting of the molded body surface tends to occur, There is a problem that the appearance of the molded body is remarkably deteriorated.

Japanese Examined Patent Publication No. 46-42236 Japanese Patent Laid-Open No. 6-322038 Japanese Patent No. 1217232 Japanese Patent No. 1340620 JP-A-11-228727

  In view of the situation as described above, an object of the present invention is to provide expandable thermoplastic resin particles suitable for pre-expansion and in-mold molding at low temperatures.

The inventors of the present invention have intensively studied to solve the above-described problems, and as a result, the monomer composition is more than 95% by weight of styrene and 99% by weight or less of styrene and 1% by weight or more and less than 5% by weight of acrylate (total of both) Expandable thermoplastic resin particles comprising a thermoplastic resin (in a quantity of 100% by weight), 696 cm ⁻¹ obtained from an infrared absorption spectrum of the thermoplastic resin pre-expanded particle surface measured by ATR-FTIR, and The absorbance ratio (A ₁₇₃₀ / A ₆₉₆ ) at ₁₇₃₀ cm ⁻¹ is 1.0 to 10 times the absorbance ratio (A ₁₇₃₀ / A ₆₉₆ ) obtained from the infrared absorption spectrum of the thermoplastic resin pre-foamed particle center. As a result, it was found that expandable thermoplastic resin particles having the above characteristics could be obtained, and the present invention was achieved.

That is,
In the first aspect of the present invention, the monomer composition is more than 95% by weight of styrene monomer and 99% by weight or less, and 1% by weight or more and less than 5% by weight of acrylate monomer (the total amount of both is 100% by weight). %) And obtained from an infrared absorption spectrum of the surface of the thermoplastic resin pre-expanded particles measured by ATR-FTIR, 696 cm ⁻¹ and 1730 cm ^−. absorbance ratio at ¹ _(a 1730 _/ a ₆₉₆₎ is not more than 10 times 1.0 times or more the absorbance ratio obtained from the infrared absorption spectrum of the thermoplastic resin pre-expanded particles center _(a 1730 _/ a ₆₉₆₎ foam Relates to a thermoplastic resin particle.
2nd of this invention is related with the foamable thermoplastic resin particle of 1st invention description whose acrylic ester is butyl acrylate.
A third aspect of the present invention relates to the expandable thermoplastic resin particles according to the first or second invention, wherein the monomer component contained in the expandable thermoplastic resin particles is less than 0.3% by weight.
4th of this invention is related with the thermoplastic resin pre-expanded particle characterized by making the foamable thermoplastic resin particle of any one of the 1st-3rd invention foam.
5th of this invention is related with the thermoplastic resin foam characterized by carrying out the shaping | molding of the thermoplastic pre-expanded particle of 4th invention.

The present invention includes a thermoplastic resin having a monomer composition of more than 95% by weight of styrene and 99% by weight or less of styrene and 1% by weight or more and less than 5% by weight of acrylate (the total amount of both is 100% by weight). a foamable thermoplastic resin particles made by the absorbance ratio at 696cm ^-1 and 1730 cm ^-1 obtained from an infrared absorption spectrum of the measured thermoplastic resin pre-expanded particle surface by _{ATR-FTIR (a 1730 / a} 696 ) Is 1.0 to 10 times the absorbance ratio (A ₁₇₃₀ / A ₆₉₆ ) obtained from the infrared absorption spectrum of the thermoplastic resin pre-foamed particle center, pre-foaming and in-mold molding at low temperature Expandable thermoplastic resin particles suitable for the above can be obtained.

The foamable thermoplastic resin particles of the present invention have a monomer composition of more than 95% by weight of styrene and 99% by weight or less of styrene and 1% by weight or more and less than 5% by weight of acrylate (the total amount of both is 100% by weight). there) a foamable thermoplastic resin particles comprising a thermoplastic resin, the absorbance at 696cm ^-1 and 1730 cm ^-1 obtained from an infrared absorption spectrum of the thermoplastic resin pre-expanded particle surface measured by ATR-FTIR When the ratio (A ₁₇₃₀ / A ₆₉₆ ) is 1.0 to 10 times the absorbance ratio (A ₁₇₃₀ / A ₆₉₆ ) obtained from the infrared absorption spectrum of the thermoplastic resin pre-foamed particle central portion, Expandable thermoplastic resin particles suitable for prefoaming and in-mold molding can be obtained.

  Examples of the styrene monomer constituting the expandable thermoplastic resin particles of the present invention include styrene derivatives such as styrene, α-methyl styrene, paramethyl styrene, t-butyl styrene, and chlorostyrene. These may be used alone or in combination of two or more.

  Examples of the acrylate monomer constituting the foamable thermoplastic resin particles of the present invention include, for example, alkyl acrylates such as methyl acrylate and butyl acrylate, methyl methacrylate, ethyl methacrylate, and cetyl methacrylate. And methacrylic acid alkyl esters. These monomers may be used independently and may be used in mixture of 2 or more types. Of these, butyl acrylate is preferred because it is easy to copolymerize with the styrene monomer and has good moldability.

The monomer composition constituting the expandable thermoplastic resin particles in the present invention is such that the monomer composition is more than 95% by weight and less than 99% by weight of the styrene monomer with respect to the total weight of 100% by weight of the charged monomers. The acrylate monomer is 1% by weight or more and less than 5% by weight, more preferably 97% by weight or more and 99% by weight or less of the styrene monomer, and 1% by weight or more and 3% by weight or less of the acrylate ester. .
In the monomer composition, when the acrylate monomer is 5% by weight or more, particularly when the foam is made highly foamed, the molded product tends to shrink, and the appearance of the molded product tends to deteriorate. is there. Moreover, when the amount of the acrylate monomer is less than 1% by weight, foaming at low temperature becomes difficult (molding with excellent heating temperature and fusing property necessary for obtaining pre-expanded particles having a desired expansion ratio. The molding temperature required to obtain the body tends to increase).
Regarding the charged monomer in the monomer composition, when the seed suspension polymerization method is carried out as a polymerization method, the monomer composition in the resin particles serving as a seed is also reflected in the charged monomer amount.

Expandable thermoplastic resin particles of the present invention, the absorbance ratio at 696cm ^-1 and 1730 cm ^-1 obtained from an infrared absorption spectrum of the measured thermoplastic resin pre-expanded particle surface by _{ATR-FTIR α (A 1730 /} A 696 ) Is 1.0 times or more and 10 times or less, preferably 1.0 times or more and 5.0 times the absorbance ratio β (A ₁₇₃₀ / A ₆₉₆ ) obtained from the infrared absorption spectrum of the thermoplastic resin pre-foamed particle central part. Is less than double.
When the ratio α / β of the absorbance ratio between the surface and the central part is higher than 10, the ratio of the acrylate ester on the particle surface is higher than the inside of the particle, particularly when molding at a high vapor pressure (high mold temperature). Surface melting tends to occur, and the surface appearance tends to be impaired. When the ratio α / β of the absorbance ratio is less than 1.0, the ratio of the acrylate ester on the particle surface becomes low, it becomes difficult to mold at a low vapor pressure (low mold temperature), and the surface appearance is deteriorated. In addition, the heating temperature at the time of preliminary foaming tends to be high.

  The absorbance ratio between the surface and the center of the thermoplastic resin pre-expanded particles can be adjusted by changing the timing of adding the acrylic ester during polymerization.

Here, the absorbance at 1730 cm ⁻¹ obtained from the infrared absorption spectrum is an absorption spectrum due to stretching vibration between C═O of the carbonyl group, and is defined as absorbance (A ₁₇₃₀ ).
The absorbance at 696 cm ⁻¹ obtained from the infrared absorption spectrum is an absorption spectrum of the out-of-plane variation angle of the aromatic benzene ring, and is defined as absorbance (A ₆₉₆ ).

  ATR-FTIR in the present invention is FTIR using an ATR (Attenuated Total Reflection) method. The ATR method is a technique in which a crystal having a high refractive index is pressure-bonded to a sample surface, the sample surface can be measured with high sensitivity using total reflection conditions, and a spectrum similar to the transmission method can be obtained easily. It is widely used for the analysis of general industrial materials such as polymer thick film, resin, coating film, paper, thread, etc.

  In general, light is not reflected at the interface between the sample and the high refractive index crystal, but is totally reflected after entering the sample side by a certain depth. At this time, although the light is totally reflected in the wave number region where the sample does not absorb, it is not totally reflected in the region where the sample is absorbed, but the intensity of the totally reflected light decreases according to the intensity of absorption. By measuring this reflected energy, a total reflection spectrum is obtained.

  However, the depth of the light penetration (measurement depth) varies greatly depending on the refractive index of the high refractive index crystal used, the refractive index of the sample, the incident angle of the measurement light, and the wave number of the measurement light, so these parameters are not specified. And the measurement results cannot be compared. The measurement depth in the ATR method is dependent on the wave number. The lower the wave number, the deeper the measurement depth and the greater the absorption intensity. Therefore, correction is required for comparison with the transmission spectrum.

In the present invention, ATR-FTIR measurement was performed under the following conditions.
High refractive index crystal species: zinc selenide (ZnSe)
Incident angle: 45 °
Measurement area: 4000 cm ^{−1 to} 600 cm ⁻¹
Detector: DLATGS
Depth of penetration: 1.66
Number of reflections: 1 time Resolution: 4 cm ⁻¹
Number of integrations: 20 times Others: An infrared absorption spectrum measured without contacting the sample was used as a background, and a process not involving the measurement spectrum was performed.

In the ATR method, the intensity of the infrared absorption spectrum obtained by measurement varies depending on the degree of adhesion between the sample and the high refractive index crystal, so that the absorbance at ₆₉₆ cm ⁻¹ (A ₆₉₆ ) is 0.08 to 0.12. In addition, the degree of adhesion between the sample and the high refractive index crystal is adjusted and measured.

  Here, when measuring the surface of the pre-expanded particles, the surface of the particles was directly adhered to the ATR prism. When measuring the central part of the pre-expanded particles, the measurement was performed by using a razor to divide into two parts so as to pass through the center of the pre-expanded particles, and to make the cross section of the divided part in close contact with the ATR prism.

From the infrared absorption spectrum obtained as described above, determine the absorbance of 698cm ^-1 _{(A 698)} and absorbance at 1730 cm ^-1 absorbance ratio of _{(A 1730) (A 698 /} A 1730). In the present invention, ATR-FTIR measurement is performed on the surface and center of any 10 pre-expanded particles, and the minimum absorbance ratio and the maximum absorbance ratio are excluded. The arithmetic average of the remaining 8 absorbance ratios was defined as the absorbance ratio (A ₆₉₆ / A ₁₇₃₀ ). From the absorbance ratio α (A ₆₉₆ / A ₁₇₃₀ ) of the obtained surface and the absorbance ratio β (A ₆₉₆ / A ₁₇₃₀ ) of the central portion, the absorbance ratio between the surface and the central portion was calculated by the following formula.
Absorbance ratio between surface and center = α (surface) / β (center)

  As a weight average molecular weight (Mw) of the expandable thermoplastic resin particle in this invention, 200,000 or more and less than 320,000 are preferable, and 220,000 or more and less than 280,000 are more preferable. If the weight average molecular weight Mw of the expandable styrene resin particles is less than 200,000, the bottom split strength tends to be low when it is formed into a foamed molded product, and if it exceeds 320,000, the foamability is low and the moldability is low. Tends to deteriorate (the heating temperature necessary for obtaining pre-expanded particles having the desired expansion ratio and the molding temperature necessary for obtaining a molded article having excellent fusing properties).

  The weight average molecular weight Mw can be controlled by a combination of the amount of the initiator used for polymerizing the thermoplastic resin particles and the polymerization temperature. For example, Mw can be lowered by increasing the amount of initiator used and / or increasing the polymerization temperature.

  In the expandable styrene resin particles of the present invention, the ratio Mw / Mn between the weight average molecular weight (Mw) and the number average molecular weight (Mn) is preferably 2.7 or more and less than 3.4. More preferably, it is less than 3.2. When Mw / Mn is less than 2.7, there is no molten particle on the surface, and there is a tendency that the molding temperature at which a good-looking molded product can be obtained tends to be low. Therefore, the moldability tends to be deteriorated (the heating temperature necessary for obtaining the pre-expanded particles having the desired expansion ratio and the molding temperature necessary for obtaining a molded article having excellent fusing property).

  The Mw / Mn ratio is controlled by a combination of the amount of initiator used when polymerizing thermoplastic resin particles and the polymerization temperature. For example, Mw / Mn can be lowered by increasing the amount of initiator used and / or increasing the polymerization temperature.

The method for producing expandable thermoplastic resin particles of the present invention includes a method of impregnating particles obtained by suspension polymerization in an aqueous medium with a foaming agent, and a foaming agent on pellets produced by bulk polymerization in an aqueous medium. It can be obtained by any of the methods of impregnating.
Among these, spherical resin particles can be obtained, and furthermore, the polymerization process and the foaming agent impregnation process can be performed consistently to obtain expandable thermoplastic resin particles. It is preferable to manufacture.
That is, as a method for producing expandable thermoplastic resin particles, a styrene monomer and an acrylate monomer are suspended, a polymerization reaction is initiated in the presence of a polymerization initiator and other additives, A method of adding a foaming agent during suspension polymerization or impregnating the foaming agent after polymerization is preferred.

  As the polymerization initiator of the monomer in the present invention, a radical generating polymerization initiator generally used for producing a thermoplastic polymer can be used. Typical polymerization initiators include, for example, azo compounds such as azobisisobutyronitrile, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, lauroyl peroxide-t-butyl. Peroxyisopropyl carbonate, 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis (t-amylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butyl) Peroxy) -3,3,5-trimethylcyclohexane, t-butyl peroxybenzoate, and other peroxides. These may be used alone or in combination of two or more.

  The amount of the polymerization initiator used in the present invention is preferably 0.01 parts by weight or more and less than 3 parts by weight with respect to 100 parts by weight of the total weight of the charged monomers. If the amount of the polymerization initiator used is less than 0.01 parts by weight, the polymerization rate tends to be slow, whereas if it exceeds 3 parts by weight, the polymerization reaction tends to be fast and difficult to control.

  Examples of the blowing agent used in the present invention include aliphatic hydrocarbons such as propane, butane, pentane and hexane, alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane, methyl chloride, dichlorodifluoromethane, and dichloro. Halogenated hydrocarbons such as tetrafluoroethane are mentioned. These foaming agents may be used alone or in combination of two or more. Among these, butane is preferable from the viewpoint of good foaming power.

  The amount of the foaming agent used in the present invention is preferably 4 parts by weight or more and less than 10 parts by weight, and more preferably 5 parts by weight or more and less than 9 parts by weight with respect to 100 parts by weight of the thermoplastic resin. When the amount of the foaming agent used is less than 4 parts by weight, the pre-foaming time becomes long and the fusion rate at the time of molding tends to decrease, resulting in an increase in production cost and economical disadvantage. When the amount of the foaming agent used is 10 parts by weight or more, the molded product tends to shrink and the appearance tends to be impaired.

Examples of the plasticizer used in the present invention include diisobutyl adipate, dioctyl adipate, dibutyl sebacate, glycerin tristearate, glycerin tricaprylate, coconut oil, palm oil, and rapeseed oil. Among these, when used for the medical field or the packaging material field that is in direct contact with food, edible oil is preferable, and palm oil, palm oil, and rapeseed oil are more preferable.
In the present invention, the plasticizer may be added in a step of polymerizing thermoplastic resin particles, a step of impregnating a foaming agent, or the like.

  The amount of the plasticizer used in the present invention is preferably 0.2 parts by weight or more and less than 2.0 parts by weight, more preferably 0.4 parts by weight or more and less than 1.6 parts by weight with respect to 100 parts by weight of the thermoplastic resin. . If the amount of the plasticizer used is less than 0.2 parts by weight, the secondary transition temperature does not decrease, which tends to be disadvantageous for pre-foaming and molding at low temperatures. It tends to be easy to do and spoil the appearance.

  The monomer component contained in the expandable thermoplastic resin particles of the present invention is less than 0.3% by weight. The contained monomer component tends to volatilize from the foamed molded product obtained by foaming the expandable thermoplastic resin particles. Particularly, when the contained monomer component is 0.3% by weight or more, the medical field Or it is unpreferable for the field of the packaging material which contacts a foodstuff directly, or for the components of a motor vehicle or a building.

  The amount of the residual monomer component is controlled by a combination of the amount of initiator used when polymerizing the thermoplastic resin particles and the polymerization temperature. For example, the residual monomer component can be lowered by increasing the amount of initiator used and / or increasing the polymerization temperature.

Examples of the suspending agent used in the present invention include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinyl pyrrolidone, and poorly soluble inorganic substances such as tricalcium phosphate and magnesium pyrophosphate.
When a hardly soluble inorganic substance is used as the suspending agent, the suspension stabilizing effect can be increased by using an anion surfactant such as sodium dodecylbenzenesulfonate.
Moreover, the combined use of a water-soluble polymer and a hardly soluble inorganic substance is also effective.

  In the present invention, in addition to the above-mentioned raw materials, materials generally used for the production of expandable thermoplastic polymer particles such as nucleating agents and flame retardants are used in combination unless the present invention is inhibited. May be.

  Examples of the nucleating agent used in the present invention include methyl methacrylate copolymer, polyethylene wax, talc, fatty acid bisamide, ethylene-vinyl acetate copolymer resin, and the like. Specific examples of the fatty acid bisamide include methylene bisstearyl amide, ethylene bisstearyl amide (hereinafter abbreviated as EBS), hexamethylene bispalmitic acid amide, ethylene bisoleic acid amide and the like.

As the flame retardant and flame retardant aid used in the present invention, known and conventional ones can be used.
Specific examples of the flame retardant include, for example, halogenated aliphatic hydrocarbon compounds such as hexabromocyclododecane, tetrabromobutane, hexabromocyclohexane, tetrabromobisphenol A, tetrabromobisphenol F, 2,4,6-tri Brominated phenols such as bromophenol, tetrabromobisphenol A-bis (2,3-dibromopropyl ether), tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A- Examples thereof include brominated phenol derivatives such as diglycidyl ether and 2,2-bis [4 ′ (2 ″, 3 ″ -dibromoalkoxy) -3 ′, 5′-dibromophenyl] -propane. These may be used alone or in combination of two or more.
Specific examples of flame retardant aids include initiators such as cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and the like. .

  The foamable thermoplastic resin particles of the present invention are pre-foamed and then heated and foamed to obtain a foamed molded product.

  As the pre-foaming method, for example, an ordinary method such as foaming by heating with steam or the like using a cylindrical pre-foaming apparatus can be employed.

  The heating temperature at the time of preliminary foaming (temperature in the can) is appropriately adjusted depending on the blowing vapor pressure and the air amount, and is usually about 101 to 105 ° C, but in the present invention, it is about 97 to 100 ° C. Pre-foaming is possible even at low temperatures.

  As a method for foam-molding the pre-foamed particles, for example, the pre-foamed particles are filled in a mold, and a foam-molded product is obtained by a method of blowing and heating steam or the like. This method can be adopted.

The blown vapor pressure at the time of molding in the mold is usually about 0.6 to 1.0 kgf / cm ² , but in the present invention, molding is possible even at about 0.3 to 0.8 kgf / cm ^2. .

  The mold temperature at the time of in-mold molding is appropriately adjusted by the blown vapor pressure, but is usually about 113 to 115 ° C., but in the present invention, molding is also performed at a lower temperature of about 109 to 115 ° C. Is possible.

  As described above, the foamable thermoplastic resin particles of the present invention can be carried out at a lower temperature than in the prior art both at the time of preliminary foaming and in-mold foam molding, and are more suitable for energy saving. is there.

  Examples and Comparative Examples are given below, but the present invention is not limited thereby. The measurement evaluation method was performed as follows.

<Measurement Method of Absorbance Ratio (A ₁₇₃₀ / A ₆₉₆ )>
The absorbance ratio of the obtained expandable thermoplastic resin particles was obtained by arbitrarily collecting 10 pre-expanded particles and analyzing the surface and the center of each pre-expanded particle under the following conditions using the ATR infrared spectroscopic analysis. To obtain an infrared absorption spectrum.
Apparatus: FTIR [manufactured by Shimadzu Corporation, FTIR-8400S] is connected to a single reflection type total reflection (ATR) measuring apparatus [manufactured by PIKE, MIRacle] ATR prism (high refractive index crystal seed): zinc selenide (ZnSe)
Incident angle: 45 °
Measurement area: 4000 cm ^{−1 to} 600 cm ⁻¹
Detector: DLATGS
Depth of penetration: 1.66
Number of reflections: 1 time Resolution: 4 cm ⁻¹
Number of integrations: 20 times Others: A process not related to the measurement spectrum was performed using the infrared absorption spectrum measured without contacting the sample as the background.
In the ATR method, the intensity of the infrared absorption spectrum obtained by measurement varies depending on the degree of adhesion between the sample and the high refractive index crystal, so that the absorbance at ₆₉₆ cm ⁻¹ (A ₆₉₆ ) is 0.08 to 0.12. In addition, the degree of adhesion between the sample and the high refractive index crystal is adjusted and measured.
Here, when measuring the surface of the pre-expanded particles, the surface of the particles was directly adhered to the ATR prism. When measuring the central part of the pre-expanded particles, the measurement was performed by using a razor to divide into two parts so as to pass through the center of the pre-expanded particles, and to make the cross section of the divided part in close contact with the ATR prism.
From the infrared absorption spectrum obtained as described above, determine the absorbance of 696cm ^-1 _{(A 696)} and absorbance at 1730 cm ^-1 absorbance ratio of _{(A 1730) (A 1730 /} A 696). In the present invention, ATR-FTIR measurement is performed on the surface and center of any 10 pre-expanded particles, and the minimum absorbance ratio and the maximum absorbance ratio are excluded. Then, the arithmetic average of the remaining 8 absorbance ratios was defined as the absorbance ratio ((A ₁₇₃₀ / A ₆₉₆ ). The obtained surface absorbance ratio α (A ₁₇₃₀ / A ₆₉₆ ) and the central portion absorbance ratio β ( (A ₁₇₃₀ / A ₆₉₆ ), the absorbance ratio between the surface and the central portion was calculated by the following formula.
Ratio of absorbance ratio between surface and center = α (surface) / β (center)

<Measurement of monomer component content>
The amount of the monomer component contained in the obtained expandable thermoplastic resin particles was obtained by dissolving 1.0 g of expandable thermoplastic resin particles in 20 ml of dichloromethane and adding 0.005 g of an internal standard solution (cyclopentanol). Then, it measured on condition of the following using gas chromatography (GC).
GC: Shimadzu Corporation GC-14B
Column: PEG-20M 25%
Chromosorb W 60/80 (3.0 m × 3.0 mm ID)
Column temperature: 110 ° C
Detector (FID) temperature: 170 ° C

<In-can temperature measurement during pre-foaming>
A thermometer was inserted from the side of a cylindrical pre-foaming machine [Daikai Kogyo, BHP], and the temperature in the can during pre-foaming was measured.

<Formability evaluation>
Using a molding machine [manufactured by Daisen, KR-57], a box-shaped mold having a thickness of 30 mm, a length of 550 mm, a width of 350 mm, and a height of 120 mm is filled, and the blowing vapor pressure is 0.3 to 0.8 kgf. In-mold molding was performed under molding conditions varied within the range of / cm ² to obtain a box-shaped foam molded product.
After the obtained thermoplastic resin foam was dried at room temperature for 24 hours, the surface property and the fusing property between the foamed particles described below both passed, and the lowest water vapor pressure was determined. It was set as a vapor pressure range in which molding was possible. Further, the mold temperature at the lowest blowing water vapor pressure and the highest blowing water vapor pressure was determined.
(1) Evaluation of fusing property The obtained thermoplastic resin foam was broken, the fracture surface was observed, and the ratio of the broken particles rather than the particle interface was determined. Sex was judged.
Pass: The rate of particle breakage is 80% or more.
Fail: The rate of particle breakage is less than 80%.
(2) Surface property evaluation The surface state of the obtained thermoplastic resin foam was visually observed, and the surface property was evaluated according to the following criteria.
Pass: Melt on the surface, little intergranularity, beautiful.
Fail: The surface is melted and there is a gap between the grains.

Example 1
<Manufacture of expandable styrene resin particles>
In a 6 liter autoclave attached to a stirrer, 100 parts by weight of pure water, 0.2 part by weight of tricalcium phosphate, 0.01 part by weight of sodium dodecylbenzenesulfonate, 0.3 part by weight of benzoyl peroxide as an initiator, and 0.21 part by weight of 1,1-bis (t-butylperoxy) cyclohexane was charged. Subsequently, 99 parts by weight of styrene monomer, 1 part by weight of butyl acrylate monomer and 1 part by weight of coconut oil were charged while stirring at 250 rpm, and the temperature was raised to 98 ° C. Then, it hold | maintained at 98 degreeC for 4 hours, and obtained the thermoplastic resin particle.
Next, 2 parts by weight of cyclohexane and 6 parts by weight of butane were injected into the autoclave as a blowing agent, and the temperature was raised to 120 ° C. again. Thereafter, the mixture was kept at 120 ° C. for 2 hours, then cooled to room temperature, and the polymerization slurry was taken out from the autoclave. The taken-out polymerization slurry was dehydrated, washed and dried to obtain expandable thermoplastic resin particles.
<Pre-foaming and manufacturing of molded products>
The obtained expandable styrene resin particles were sieved to a particle diameter of 0.6 mm to 1.2 mm. The foamable styrene-based resin particles thus screened were prefoamed at a bulk magnification of 65 times under the condition of a blowing vapor pressure of 0.8 kgf / cm ² using a pressure prefoaming machine (manufactured by Daikai Kogyo Co., Ltd., BHP). . At this time, air was blown into the blown steam to adjust the blown steam temperature. As a result, the pressure heating time was 70 seconds, and the temperature inside the can was 99 ° C. Then, it was left to stand at room temperature for 1 day, and curing drying was performed.
Next, the obtained thermoplastic resin pre-expanded particles are placed in a box-shaped mold having a thickness of 30 mm, a length of 550 mm, a width of 350 mm, and a height of 120 mm, using a molding machine [manufactured by Daisen, KR-57]. Filling and in-mold molding were performed under the molding conditions of a blowing vapor pressure of 0.3 to 0.8 kgf / cm ² to obtain a box-shaped foam molded product.
The moldable vapor pressure range was 0.3 to 0.8 kgf / cm ² , and the mold temperature at that time was 109 to 115 ° C.
Evaluation was performed using the obtained foamable thermoplastic resin particles and foamed molded article, and the results are shown in Table 1.

(Example 2)
<Manufacture of expandable styrene resin particles>
Expandable thermoplastic resin particles were obtained in the same manner as in Example 1, except that the monomer composition at the start of polymerization was changed to 98 parts by weight of styrene monomer and 2 parts by weight of butyl acrylate monomer.
<Pre-foaming and manufacturing of molded products>
When obtaining pre-expanded particles having a bulk magnification of 65 times, the pressure heating time at the time of pre-expansion was 63 seconds, and the temperature in the can was 98 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.8 kgf / cm ² , and the mold temperature at that time is 109 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Example 3)
<Manufacture of expandable styrene resin particles>
Expandable thermoplastic resin particles were obtained in the same manner as in Example 1, except that the monomer composition at the start of polymerization was changed to 97 parts by weight of styrene monomer and 3 parts by weight of butyl acrylate monomer.
<Pre-foaming and manufacturing of molded products>
When pre-expanded particles having a bulk magnification of 65 times were obtained, the pressure heating time at the time of pre-expansion was 55 seconds, and the temperature in the can was 98 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.8 kgf / cm ² , and the mold temperature at that time is 109 to 115 ° C. It was. The evaluation results are shown in Table 1.

( Comparative Example 7 )
<Manufacture of polystyrene resin seed particles>
In a reactor equipped with a stirrer, 100 parts by weight of pure water, 0.4 parts by weight of tribasic calcium phosphate, 0.01 parts by weight of sodium dodecylbenzenesulfonate, and 0.5 parts by weight of sodium chloride were stirred and suspended in water. Then, 0.2 parts by weight of benzoyl peroxide and 0.2 parts by weight of 1,1-bis (t-butylperoxy) cyclohexane are dissolved in 100 parts by weight of styrene as a polymerization initiator and added to the reactor. The temperature was raised to 98 ° C., and polymerization was performed over 4.5 hours. Next, the temperature was raised to 110 ° C. and held for 1 hour, followed by cooling. The contents were taken out, dehydrated and dried, and sieved to obtain polystyrene resin seed particles having a particle size of 0.425 to 0.500 mm. .
<Manufacture of expandable styrene resin particles>
In polymerization of thermoplastic resin particles, 87 parts by weight of water in a 6 L autoclave, 0.6 parts by weight of tricalcium phosphate, 0.01 parts by weight of α-olefin sulfonate, 10 parts by weight of the resulting polystyrene resin seed particles And a solution in which 0.1 part by weight of benzoyl peroxide and 0.1 part by weight of 1,1-bis (t-butylperoxy) cyclohexane as a polymerization initiator were dissolved in 10 parts by weight of styrene was added. Thereafter, the aqueous suspension was heated to 90 ° C. and maintained for 30 minutes to impregnate the polystyrene resin particles with the styrene solution.
Further, while maintaining at 90 ° C. and stirring, 60 parts by weight of styrene monomer and 0.3 part by weight of benzoyl peroxide were added dropwise to the reaction system over 5 hours, followed by polymerization, and then 17 parts by weight of styrene monomer. And 3 parts by weight of butyl acrylate were dropped into the reaction system over 2 hours for polymerization, and then held at 90 ° C. for 1 hour to obtain thermoplastic resin particles.
Subsequently, the operations after the impregnation with the foaming agent were carried out in the same manner as in Example 1 to obtain expandable thermoplastic resin particles.
<Pre-foaming and manufacturing of molded products>
When obtaining pre-expanded particles having a bulk magnification of 65 times, the pressure heating time at the time of pre-expansion was 53 seconds, and the temperature in the can was 98 ° C.
Next, the vapor pressure range in which molding is possible is 0.3 to 0.6 kgf / cm ² in the same way as in Example 1, and the mold temperature at that time is 109 to 113 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 1)
<Manufacture of expandable styrene resin particles>
In the polymerization of the thermoplastic resin particles, a foamable thermoplastic resin was obtained by the same operation as in Example 1 except that the monomer composition was changed to 100 parts by weight of styrene monomer without using a butyl acrylate monomer at the start of polymerization. Particles were obtained.
<Pre-foaming and manufacturing of molded products>
To obtain a bulk magnification 65 times the pre-expanded particles, a result of changing the blowing vapor pressure during prefoaming from 0.8 kgf / cm ² to 1.0 kgf / cm ^2, pressurizing and heating time is 97 seconds, the temperature in the reactor Was 103 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding as in Example 1 is 0.6 to 0.8 kgf / cm ² , and the mold temperature at that time is 113 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 2)
<Manufacture of expandable styrene resin particles>
Expandable thermoplastic resin particles were obtained in the same manner as in Example 1, except that the monomer composition at the start of polymerization was changed to 95 parts by weight of styrene monomer and 5 parts by weight of butyl acrylate monomer.
<Pre-foaming and manufacturing of molded products>
When obtaining pre-expanded particles having a bulk magnification of 65 times, the pressure heating time at the time of pre-expansion was 34 seconds, and the temperature in the can was 97 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.3 to 0.4 kgf / cm ² , and the mold temperature at that time is 109 to 110 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 3)
<Manufacture of polystyrene resin seed particles>
By the same operation as in Example 4, polystyrene resin seed particles having a particle size of 0.425 to 0.500 mm were obtained.
<Manufacture of expandable styrene resin particles>
In polymerization of thermoplastic resin particles, in a 6 L autoclave, 87 parts by weight of water, 0.6 parts by weight of tricalcium phosphate, 0.01 parts by weight of sodium α-olefin sulfonate, and the resulting polystyrene resin seed particles 10 Suspended parts by weight, 8 parts by weight of styrene and 2 parts by weight of butyl acrylate, 0.1 part by weight of benzoyl peroxide as a polymerization initiator and 0.1 part by weight of 1,1-bis (t-butylperoxy) cyclohexane A solution in which was dissolved was added. Thereafter, the obtained aqueous suspension was heated to 90 ° C. and maintained for 30 minutes, whereby polystyrene resin particles were impregnated with a styrene solution.
Furthermore, while maintaining at 90 ° C. and stirring, 80 parts by weight of styrene monomer and 0.3 part by weight of benzoyl peroxide were dropped into the reaction system over 7 hours, followed by polymerization, and then at 90 ° C. for 1 hour. This was retained to obtain thermoplastic resin particles.
Subsequently, the operations after the impregnation with the foaming agent were carried out in the same manner as in Example 1 to obtain expandable thermoplastic resin particles.
<Pre-foaming and manufacturing of molded products>
To obtain a bulk magnification 65 times the pre-expanded particles, a result of changing the blowing vapor pressure during prefoaming from 0.8 kgf / cm ² to 1.0 kgf / cm ^2, pressurizing and heating time is 68 seconds, the temperature in the reactor Was 101 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.4 to 0.8 kgf / cm ² , and the mold temperature at that time is 110 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 4)
<Manufacture of polystyrene resin seed particles>
By the same operation as in Example 4, polystyrene resin seed particles having a particle size of 0.425 to 0.500 mm were obtained.
<Manufacture of expandable styrene resin particles>
In polymerization of thermoplastic resin particles, in a 6 L autoclave, 87 parts by weight of water, 0.6 parts by weight of tricalcium phosphate, 0.01 parts by weight of sodium α-olefin sulfonate, and the resulting polystyrene resin seed particles 10 Suspend parts by weight and add a solution of 0.1 part by weight of benzoyl peroxide and 0.1 part by weight of 1,1-bis (t-butylperoxy) cyclohexane as a polymerization initiator to 10 parts by weight of styrene did. Thereafter, the obtained aqueous suspension was heated to 90 ° C. and maintained for 30 minutes, whereby polystyrene resin particles were impregnated with a styrene solution.
Further, while maintaining the temperature at 90 ° C. and stirring, 70 parts by weight of styrene monomer and 0.3 part by weight of benzoyl peroxide were dropped into the reaction system over 6 hours, followed by polymerization, and then 7% by weight of styrene monomer. And 3 parts by weight of butyl acrylate were added dropwise to the reaction system over 1 hour for polymerization, and then held at 90 ° C. for 1 hour to obtain thermoplastic resin particles.
Subsequently, the operations after the impregnation with the foaming agent were carried out in the same manner as in Example 1 to obtain expandable thermoplastic resin particles.
<Pre-foaming and manufacturing of molded products>
When pre-expanded particles having a bulk magnification of 65 times were obtained, the pressure heating time at the time of pre-expansion was 51 seconds, and the temperature in the can was 98 ° C.
Next, the vapor pressure range in which molding is possible is 0.3 to 0.5 kgf / cm ² in the same way as in Example 1, and the mold temperature at that time is 109 to 111 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 5)
<Manufacture of polystyrene resin seed particles>
By the same operation as in Example 4, polystyrene resin seed particles having a particle size of 0.425 to 0.500 mm were obtained.
<Manufacture of expandable styrene resin particles>
In polymerization of thermoplastic resin particles, in a 6 L autoclave, 87 parts by weight of water, 0.6 parts by weight of tricalcium phosphate, 0.01 parts by weight of sodium α-olefin sulfonate, and the resulting polystyrene resin seed particles 10 Suspend parts by weight and add a solution of 0.1 part by weight of benzoyl peroxide and 0.1 part by weight of 1,1-bis (t-butylperoxy) cyclohexane as a polymerization initiator to 10 parts by weight of styrene did. Thereafter, the obtained aqueous suspension was heated to 90 ° C. and maintained for 30 minutes, whereby polystyrene resin particles were impregnated with a styrene solution.
Further, while maintaining at 90 ° C., with stirring, 79.6 parts by weight of styrene monomer, 0.4 part by weight of butyl acrylate and 0.3 part by weight of benzoyl peroxide are dropped into the reaction system over 6 hours to polymerize. After that, it was kept at 90 ° C. for 1 hour to obtain thermoplastic resin particles.
Subsequently, the operations after the impregnation with the foaming agent were carried out in the same manner as in Example 1 to obtain expandable thermoplastic resin particles.
<Pre-foaming and manufacturing of molded products>
To obtain a bulk magnification 65 times the pre-expanded particles, a result of changing the blowing vapor pressure during prefoaming from 0.8 kgf / cm ² to 1.0 kgf / cm ^2, pressurizing and heating time is 82 seconds, the temperature in the reactor Was 102 ° C.
Next, the vapor pressure range that can be molded when in-mold molding was performed in the same manner as in Example 1 was 0.5 to 0.8 kgf / cm ² , and the mold temperature at that time was 112 to 115 ° C. It was. The evaluation results are shown in Table 1.

(Comparative Example 6)
<Manufacture of polystyrene resin seed particles>
By the same operation as in Example 4, polystyrene resin seed particles having a particle size of 0.425 to 0.500 mm were obtained.
<Manufacture of expandable styrene resin particles>
In polymerization of thermoplastic resin particles, in a 6 L autoclave, 87 parts by weight of water, 0.6 parts by weight of tricalcium phosphate, 0.01 parts by weight of sodium α-olefin sulfonate, and the resulting polystyrene resin seed particles 10 Suspended parts by weight, 9 parts by weight of styrene and 1 part by weight of butyl acrylate 0.1 parts by weight of benzoyl peroxide and 0.1 part by weight of 1,1-bis (t-butylperoxy) cyclohexane as a polymerization initiator A solution in which was dissolved was added. Thereafter, the obtained aqueous suspension was heated to 90 ° C. and maintained for 30 minutes, whereby polystyrene resin particles were impregnated with a styrene solution.
Furthermore, while maintaining at 90 ° C. and stirring, 80 parts by weight of styrene monomer and 0.3 part by weight of benzoyl peroxide were dropped into the reaction system over 7 hours, followed by polymerization, and then at 90 ° C. for 1 hour. Retained thermoplastic resin particles were obtained.
Subsequently, the operations after the impregnation with the foaming agent were carried out in the same manner as in Example 1 to obtain expandable thermoplastic resin particles.
<Pre-foaming and manufacturing of molded products>
To obtain a bulk magnification 65 times the pre-expanded particles, a result of changing the blowing vapor pressure during prefoaming from 0.8 kgf / cm ² to 1.0 kgf / cm ^2, pressurizing and heating time is 75 seconds, the temperature in the reactor Was 101 ° C.
Next, the vapor pressure range that can be molded when performing in-mold molding in the same manner as in Example 1 is 0.4 to 0.8 kgf / cm ² , and the mold temperature at that time is 110 to 115 ° C. It was. The evaluation results are shown in Table 1.

Claims (4)

Heat having a monomer composition of more than 95% by weight of styrene monomer and 99% by weight or less of styrene monomer and 1% by weight or more and less than 5% by weight of acrylate monomer (the total amount of both is 100% by weight) Expandable thermoplastic resin particles comprising a plastic resin,
Absorbance ratio at 696cm ^-1 and 1730 cm ^-1 obtained from an infrared absorption spectrum of the measured thermoplastic resin pre-expanded particle surface by _{ATR-FTIR α (A 1730 /} A 696) is a thermoplastic resin pre-expanded particles center 1.0 Baidea absorbance ratio obtained from infrared absorption spectrum β (a ₁₇₃₀ / a ₆₉₆₎ is, and
Monomer component contained in the expandable thermoplastic resin particles are characterized in der Rukoto less than 0.3 wt%, expandable thermoplastic resin particles.   2. The expandable thermoplastic resin particles according to claim 1, wherein the acrylate is butyl acrylate. A thermoplastic resin pre-expanded particle obtained by foaming the expandable thermoplastic resin particle according to claim 1 or 2 . A thermoplastic resin foam obtained by in-mold molding of the thermoplastic pre-expanded particles according to claim 3 .