WO2020184007A1 - Foamable resin particles, pre-foamed particles, and shaped foam - Google Patents

Abstract

The present invention addresses the problem of providing foamable resin particles that have a low VOC content and in which VOC off-gassing levels can be suppressed. This goal is achievable through foamable resin particles containing: a base resin comprising a styrene unit and an acrylonitrile unit as constituent units; and a foaming agent, wherein the ratio D2230/D1600 of absorbance at wavelength 2230 cm^–1 and wavelength 1600 cm^–1 in the infrared absorption spectrum of the surfaces of foam particles obtained by foaming the foamable resin particles is 0.8 or higher.

Description

Foamable resin particles, prefoamed particles, and foamed molded article

The present invention relates to foamable resin particles, pre-foamed particles, and a foamed molded product, which have a low content of volatile organic compounds and can suppress the emission amount of approximately volatile organic compounds.

Foamable polystyrene resin particles are well known as foamable resin particles. Foamable polystyrene resin particles are widely used because they can be easily obtained by in-mold foam molding and are inexpensive.

While foamable polystyrene resin particles are excellent in light weight and heat insulating performance, they are contained in volatile organic compounds (hereinafter, sometimes referred to as "VOC" by taking the acronym of Volatile Organic Compounds in English) per unit time. The problem was that the amount of radiation was large. Especially for foamable polystyrene resin particles, it is difficult for both styrene and ethylbenzene, which are VOC components, to meet the strict emission standards in the fields of automobiles and building materials, and it is necessary to take measures such as drying the foamed molded product for several days. , It is one of the causes of cost increase.

In order to solve the above problems, in Patent Documents 1 and 2, foamable polystyrene resin particles having a small amount of residual styrene in the resin particles are provided by devising a manufacturing method such as increasing the number of copies of the initiator added and / or adding the flame retardant afterwards. It is disclosed that it can be provided.

Further, Patent Document 3 discloses styrene / acrylonitrile / alpha-methylstyrene-based heat-resistant styrene-based resin particles produced by using the initiator described in Patent Document 1 or a similar initiator of the initiator.

JP-A-2017-052894 JP-A-2010-195936 JP 2016-164213

The above-mentioned conventional technique was improved from the viewpoint of reducing the amount of VOC emission from the viewpoint of general foamable resin particles at the technical level at the time of development of the conventional technique. However, there is a great deal of interest in reducing VOC emissions in the market, and the prior art as described above has room for further improvement in terms of VOC emissions (particularly styrene and ethylbenzene).

One embodiment of the present invention has been made in view of the above problems, and an object of the present invention is to have a small VOC content and its emission amount, a novel foamable resin particle, and a small VOC emission amount and its emission amount. Is to provide a new foam molded product.

As a result of diligent studies, the present inventors have completed the present invention. That is, the foamable resin particles according to the embodiment of the present invention are foamable resin particles containing a base resin containing a styrene unit and an acrylonitrile unit as a constituent unit and a foaming agent, and the foamable resin particles are used. red absorbance ratio at a wavelength of 2230 cm ^-1 and a wavelength 1600 cm ^-1 in the infrared absorption spectrum D2230 / D1600 of foamed was foamed particle surface is 0.80 or more.

Further, the method for producing foamable resin particles according to an embodiment of the present invention is a method for producing foamable resin particles, which is a copolymerization in which a monomer containing a styrene monomer and an acrylonitrile monomer is copolymerized. The first step includes a step and a step of impregnating the obtained copolymer with a foaming agent, and the copolymerization step includes a continuous first polymerization step and a second polymerization step having different polymerization temperatures. In the polymerization step, a polymerization initiator containing a polymerization initiator (X) having a 10-hour half-life temperature of 74 ° C. or higher and 94 ° C. or lower is used, and the polymerization initiator (X) contains benzoyl peroxide and is foamed. The TH / TQ ratio of the sex resin particles is less than 1.20.

In one embodiment of the present invention, foamable resin particles, pre-foamed particles (foamed particles), and a foamed molded product, which have a low content of volatile organic compounds (VOC) and can suppress the emission amount of approximately volatile organic compounds (VOC). Can be provided.

It is a graph which shows an example of the GPC measurement chart of the foamable resin particle.

An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications can be made within the scope of the claims. The technical scope of the present invention also includes embodiments or examples obtained by appropriately combining the technical means disclosed in the different embodiments or examples.

Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. In addition, all the academic documents and patent documents described in the present specification are incorporated as references in the present specification. Further, unless otherwise specified in the present specification, "A to B" representing a numerical range is intended to be "A or more (including A and larger than A) and B or less (including B and smaller than B)".

<Effervescent resin particles>
The foamable resin particles according to the embodiment of the present invention are foamable resin particles containing a base resin containing a styrene unit and an acrylonitrile unit as a constituent unit and a foaming agent, and the foamable resin particles are foamed. red absorbance ratio at a wavelength of 2230 cm ^-1 and a wavelength 1600 cm ^-1 in the infrared absorption spectrum D2230 / D1600 of the foamed particle surface, characterized in that at least 0.80. The infrared absorption spectrum in one embodiment of the present invention can be obtained by ATR-FTIR analysis.

In the present specification, the "infrared absorption spectrum on the surface of foamed particles" is intended as "infrared absorption spectrum obtained by Fourier transform infrared spectroscopic analysis on the surface of foamed particles by total reflection measurement method". In the present specification, "Fourier transform infrared spectroscopic analysis by total reflection measurement method" may be referred to as "ATR-FTIR analysis".

In one embodiment of the present invention, the foamed particles used for measuring the infrared absorption spectrum are obtained by treating the foamable resin particles according to the embodiment of the present invention in the following order (1) to (3). (1) The foamable resin particles are put into a pressurized foaming machine; (2) Next, steam is blown into the foaming machine at a blowing vapor pressure of 0.09 MPa to 0.10 MPa, and the pressure inside the foaming machine is adjusted. By preparing in the range of 0.01 MPa to 0.02 MPa, the temperature inside the foaming machine is set to 100 ° C. to 104 ° C., whereby the foamed particles are foamed at a magnification of 40 times; (3) Next, the obtained foaming The particles are cured at 25 ° C. for 12 to 24 hours to obtain foamed particles used for measuring the infrared absorption spectrum.

The foamable resin particles according to the embodiment of the present invention have an advantage that a foamed molded product having a small amount of VOC emission can be provided by having the above structure. As a result, it is possible to clear the standard of VOC emission amount required in the fields of automobiles and building materials. That is, the foamable resin particles according to the embodiment of the present invention have an advantage that a highly productive foamed molded product can be provided.

Here, for the foamable resin particles according to the embodiment of the present invention, the foamable resin particles are used to produce foamed particles by a known method, and the foamed resin particles are foam-molded by a known method. Can provide a foam molded article.

In the present specification, "foamable resin particles according to one embodiment of the present invention" may be simply referred to as "present foamable resin particles". That is, the term "the present foamable resin particles" is intended to be an embodiment of the foamable resin particles in the present invention.

In a broad sense, VOC means, for example, as defined by the Air Pollution Control Act of Japan, "organic compounds that are gas when they are discharged into the atmosphere from the outlet and scattered." In each technical field, compounds to be regulated as VOCs are specified. For example, the Ministry of Health, Labor and Welfare of Japan has established indoor concentration guideline values for the following substances: formaldehyde, acetaldehyde, toluene, ethylbenzene, xylene, styrene, nonanal, tetradecane, di-n-butyl phthalate, di-butyl phthalate. 2-Ethylhexyl, p-dichlorobenzene, chloropyriphos, diazinon, and phenocarb. In addition, the Automobile Manufacturers Association regulates the concentrations of the following substances in the vehicle interior: formaldehyde, acetaldehyde, toluene, ethylbenzene, xylene, styrene, tetradecane, di-n-butyl phthalate, and di-2-ethylhexyl phthalate. ..

In the present specification, VOC means "among compounds that can be contained in foamable resin particles or foamed molded articles, (a) a gas when discharged into the atmosphere and scattered, and (b) the Ministry of Health, Labor and Welfare of Japan. Is intended as an "organic compound for which the indoor concentration guideline value is set." Specifically, VOCs herein are intended to be styrene and ethylbenzene.

The base resin contained in the foamable resin particles contains a styrene unit and an acrylonitrile unit as constituent units. In the present specification, the "styrene unit" is a structural unit derived from a styrene monomer, and the "acrylonitrile unit" is a structural unit derived from an "acrylonitrile monomer".

In the base resin contained in the foamable resin particles, (a) the content of the styrene unit is 55 parts by weight or more and 80 parts by weight or less, and the content of the acrylonitrile unit is 20 parts by weight or more and 45 parts by weight or less. (B) The total content of the styrene unit and the acrylonitrile unit is preferably 100 parts by weight.

The content of the styrene unit is preferably 55 parts by weight or more and 80 parts by weight or less, more preferably 60 parts by weight or more and 80 parts by weight or less, and more preferably 65 parts by weight or more and 75 parts by weight or less. When the content of the styrene unit is (a) 55 parts by weight or more, the foamable resin particles are excellent in moldability, and (b) when it is 80 parts by weight or less, the foamable resin particles are excellent in heat resistance. A foam molded product can be provided.

The content of the acrylonitrile unit is preferably 20 parts by weight or more and 45 parts by weight or less, more preferably 20 parts by weight or more and 40 parts by weight or less, and more preferably 25 parts by weight or more and 35 parts by weight or less. When the content of the acrylonitrile unit is 20 parts by weight or more, the foamable resin particles are (a) excellent in gas barrier property, so that the amount of styrene released as VOC is small, and (b) excellent in heat resistance. Can be provided. When the content of the acrylonitrile unit is 45 parts by weight or less, the foamable resin particles are excellent in moldability, and the polymerization stability is increased during the production of the foamable resin particles.

The foamable resin particles according to the embodiment of the present invention have an absorbance at 2230 cm- ¹ in the infrared absorption spectrum obtained by ATR-FTIR analysis on the surface of the foamed particles obtained by foaming the foamable resin particles. The absorbance D1600 at D2230 and 1600 cm ^-1 is determined, and the absorbance ratio of D2230 / D1600 is 0.8 or more. The preferable range of the absorbance ratio of D2230 / D1600 is 1.2 or more and 2.5 or less. When the absorbance ratio of D2230 / D1600 is 0.8 or more, the VOC component emitted from the foamed molded product can be significantly suppressed.

In the present specification, "ATR-FTIR analysis" is intended as "Fourier transform infrared spectroscopic analysis by total reflection measurement method".

The base resin contained in the foamable resin particles may further contain an alpha-methylstyrene unit as a constituent unit. Since the glass transition temperature of the base resin rises when alpha-methylstyrene is added, the foamable resin particles can provide a foamed molded product having sufficient heat resistance.

In the present specification, the "alpha-methylstyrene unit" is a structural unit derived from an alpha-methylstyrene monomer.

The content of the alphamethylstyrene unit is preferably 3 parts by weight or more and 15 parts by weight or less, more preferably, when the total content of the styrene unit, the acrylonitrile unit and the alphamethylstyrene unit in the base resin is 100 parts by weight. It is 4 parts by weight or more and 10 parts by weight or less, and more preferably 4 parts by weight or more and 7 parts by weight or less. Alpha-methylstyrene has a methyl group at the alpha position and is characterized by large steric hindrance and therefore poor reactivity. Further, when alpha-methylstyrene is contained in the base resin, the alpha-methylstyrene moiety in the base resin is easily decomposed. Therefore, when the content of the alpha-methylstyrene unit is 3 parts by weight or more, the polymerization rate does not become too high during the production of the foamable resin particles, so that the polymerization can be easily controlled. Further, when the content of the alphamethylstyrene unit is 15 parts by weight or less, (a) the obtained base resin is difficult to decompose, so that the foamable resin particles can provide a foamed molded product having excellent flame retardancy. b) Since the reactivity during the polymerization reaction does not deteriorate, the weight average molecular weight of the obtained base resin does not become too low, and (c) the foamable resin particles have a low styrene content as VOC.

In the base resin contained in the foamable resin particles, the content of (a) and (a-1) styrene units is 55 parts by weight or more and 80 parts by weight or less, and the content of acrylonitrile units is 20 parts by weight or more and 45 parts by weight. The content of the alphamethylstyrene unit is 0 parts by weight or more and 15 parts by weight or less, and the total content of (a-2) styrene unit, acrylonitrile unit and alphamethylstyrene unit is 100 parts by weight. (B) (b-1) The content of the styrene unit is 60 parts by weight or more and 80 parts by weight or less, the content of the acrylonitrile unit is 20 parts by weight or more and 40 parts by weight or less, and the alphamethylstyrene unit. The content is preferably 0 parts by weight or more and 15 parts by weight or less, and the total content of (b-2) styrene unit, acrylonitrile unit and alphamethylstyrene unit is preferably 100 parts by weight, and (c) (c-). 1) The content of styrene unit is 60 parts by weight or more and 75 parts by weight or less, the content of acrylonitrile unit is 21 parts by weight or more and 27 parts by weight or less, and the content of alphamethylstyrene unit is 3 parts by weight or more and 15 parts by weight. More preferably, the total content is 100 parts by weight or less and the total content of (c-2) styrene unit, acrylonitrile unit and alphamethylstyrene unit is 100 parts by weight.

The foaming agents contained in the effervescent resin particles include (a) aliphatic hydrocarbons such as hydrocarbons such as propane, isobutane, normal butane, isopentane, normal pentane, and neopentanecyclohexane, and (b) difluoroethane. , And volatile foaming agents such as fluorinated hydrocarbons having a zero ozone destruction coefficient, such as tetrafluoroethane, but are not limited thereto. The above-mentioned foaming agent may be used alone or in combination of two or more.

The content of the foaming agent in the foamable resin particles is preferably 2 parts by weight or more and 7 parts by weight or less with respect to 100 parts by weight of the foamable resin particles, and more preferably 3 parts by weight or more and 6 parts by weight or less. It is preferably 4 parts by weight or more and 5 parts by weight or less. According to the above configuration, (a) foamable resin particles can be used to produce foamed particles having a foaming ratio of 40 times or more, and (b) foamable resin particles are foam-molded with excellent heat resistance and flame retardancy. Can provide the body.

The foamable resin particles may optionally contain other additives in addition to the base resin and the foaming agent. Examples of the other additives include plasticizers, bubble modifiers, flame retardants, flame retardants, heat ray radiation inhibitors, pigments, dyes and antistatic agents.

Examples of the plasticizer include high boiling point plasticizers having a boiling point of 200 ° C. or higher. Examples of such plasticizers include (a) fatty acid glycerides such as (a) triglyceride stearate, triglyceride palmitate, triglyceride laurate, diglyceride stearate, and monoglyceride stearate, and (b) coconut oil, palm oil, and palm kernel oil. Vegetable oils, (c) aliphatic esters such as dioctyl adipate and dibutyl sebacate, and (d) organic hydrocarbons such as liquid paraffin and cyclohexane. When the foamable resin particles contain a large amount of the substances listed as these plasticizers, the heat resistance of the foamed molded product that the foamable resin particles can provide tends to deteriorate. Therefore, the content of the plasticizer in the foamable resin particles can be appropriately set so that the foamed molded product that the foamable resin particles can provide has desired heat resistance.

The foamable resin particles may contain a bubble adjusting agent in order to adjust the bubble diameter in the foamed molded product that the foamable resin particles can provide. Examples of the bubble adjusting agent include (a) aliphatic bisamides such as methylene bisstearic acid amide and ethylene bisstearic acid amide, and (b) polyethylene wax. The content of the bubble modifier in the foamable resin particles is preferably less than 0.1 parts by weight with respect to 100 parts by weight of the foamable resin particles. According to the above configuration, in the foamed molded product that the foamable resin particles can provide, deterioration of heat resistance and an increase in VOC emission amount due to miniaturization of bubbles do not occur.

The foamable resin particles may contain a flame retardant in order for the foamed molded product that the foamable resin particles can provide to obtain flame retardancy. As the flame retardant, a brominated flame retardant is preferable. As brominated flame retardants, 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 copolymers. Since the foamed molded product that the foamable resin particles can provide tends to obtain flame retardancy, the present foamable resin particles can be used as a flame retardant with 2,2-bis [4'-(2'', 3''-). It preferably contains dibromo-2''-methylpropyloxy)-, 3', 5'-dibromophenyl] -propane. In addition, 2,2-bis [4'-(2'', 3''-dibromo-2''-methylpropyloxy)-, 3', 5'-dibromophenyl] -propane is tetrabromobisphenol A-. Also referred to as bis (2,3-dibromo-2-methylpropyl) ether.

The content of the flame retardant in the foamable resin particles is preferably 1.5 parts by weight or more and 3.0 parts by weight or less with respect to 100 parts by weight of the foamable resin particles, and is 1.8 parts by weight or more and 2.5 parts by weight. It is more preferably less than parts by weight. When the content of the flame retardant in the foamable resin particles is (a) 1.5 parts by weight or more with respect to 100 parts by weight of the foamable resin particles, the foamed molded article that the foamable resin particles can provide is sufficiently difficult. When the fuel performance can be obtained and (b) 3.0 parts by weight or less, the foamable resin particles have a low VOC content and are excellent in moldability.

When the foamable resin particles contain a flame retardant, the foamable resin particles preferably further contain a flame retardant aid. As the flame retardant aid, a radical generator such as a peroxide can be used. Examples of such radical generators include dicumyl peroxide, t-butyl peroxybenzoate, 2,3-dimethyl-2,3-diphenylbutane, and 3,4-dialkyl-3,4-diphenylhexane. Be done. Since it is possible to provide a foamed molded product having a small effect on the polymerization reaction and having good flame retardant performance, the foamable resin particles can be used as a flame retardant aid at a 10-hour half-life temperature of 130 ° C. or higher and 150 ° C. or lower. It is more preferable to contain a certain peroxide, and it is particularly preferable to contain a dicumyl peroxide.

The content of the flame retardant aid in the foamable resin particles is preferably 0.3 parts by weight or more and 1.5 parts by weight or less with respect to 100 parts by weight of the foamable resin particles. When the content of the flame retardant in the foamable resin particles is (a) 0.3 parts by weight or more with respect to 100 parts by weight of the foamable resin particles, the foamed molded article that the foamable resin particles can provide is sufficiently difficult. When it has fuel performance and (b) 1.5 parts by weight or less, the foamed molded product that the foamable resin particles can provide has sufficient heat resistance.

The content of styrene in the foamable resin particles is preferably less than 20 ppm, and the content of ethylbenzene is preferably 130 ppm or less. The content of styrene in the foamable resin particles is more preferably 10 ppm or less, still more preferably 5 ppm or less. Especially preferably, it is 0 ppm or less. 0 ppm means below the detection limit in gas chromatography. The content of ethylbenzene in the foamable resin particles is more preferably 100 ppm or less, still more preferably 70 ppm or less. According to the above configuration, the foamed molded product that the foamable resin particles can provide can reduce the amount of VOC emitted into the environment, and as a result, it is possible to suppress an adverse effect on the human body. Here, the content of styrene in the foamable resin particles is intended to be the content of the styrene monomer in the foamable resin particles, and the content of ethylbenzene in the foamable resin particles is foamable. The content of ethylbenzene monomer in the resin particles is intended. Examples of the method for measuring the content of styrene and ethylbenzene (that is, the VOC content) in the foamable resin particles include a measurement method using gas chromatography. A specific method will be described in Examples described later.

The weight average molecular weight of the base resin of the foamable resin particles is preferably 150,000 or more and 220,000 or less, and more preferably 170,000 or more and 200,000 or less. When the weight average molecular weight of the base resin is (a) 150,000 or more, the foamed molded product that the foamable resin particles can provide has sufficient strength, flame retardancy, and heat resistance, and (b). ) When it is 220,000 or less, it has sufficient foaming power and the moldability of the foamable resin particles is good. Examples of the method for measuring the weight average molecular weight of the base resin include a measuring method using gel permeation chromatography.

The foamable resin particles preferably have a weight average molecular weight of 150,000 or more and 220,000 or less, and more preferably 170,000 or more and 200,000 or less. When the weight average molecular weight of the foamable resin particles is (a) 150,000 or more, the foamed molded product that the obtained foamable resin particles can provide has sufficient strength, flame retardancy, and heat resistance. , (B) When it is 220,000 or less, it has sufficient foaming power and the moldability of the foamable resin particles is good. Examples of the method for measuring the weight average molecular weight of the foamable resin particles include a measuring method using gel permeation chromatography.

(TH / TQ ratio of foamable resin particles)
The TH / TQ ratio of the foamable resin particles will be described. GPC measurement is performed on the foamable resin particles using gel permeation chromatography to obtain a GPC measurement chart. Here, the GPC measurement chart is a chart of the relationship between the molecular weight and the differential distribution value, and is obtained as a graph in which the horizontal axis is the molecular weight and the vertical axis is the differential distribution value. Here, the horizontal axis is represented by a logarithm (Log). An example of a GPC measurement chart of foamable resin particles is shown in FIG.

FIG. 1 is a diagram showing an example of a GPC measurement chart of foamable resin particles. The point where the integrated distribution value on the GPC curve of the GPC measurement chart is the highest is set as the peak top, and is set as the point P as shown in FIG. Then, through the point P (peak top), draw a line L ₁ perpendicular to the horizontal axis of the graph. Line L ₁ and intersection next point P of the GPC curve, the intersection of the lines L ₁ and the horizontal axis of the graph as point S. Regarding the line segment PS, the point corresponding to the length of 2/3 of the line segment PS from the point P is defined as the point T. That is, the length of the line segment ST is twice the length of the line segment PT. Then, through the point T, draw a line parallel L ₂ on the horizontal axis of the graph. Of two intersections between the line L ₂ and the GPC curve, the intersection of the left side (lower molecular weight) and the point Q than the line L _1, and the point H to the intersection of the right side (high molecular weight side) than the line L ₁ .. The ratio of the length of the line segment TQ to the length of the line segment TH is defined as the TH / THQ ratio. The larger the TH / TQ ratio, the larger the high molecular weight component of the foamable resin particles. In the production of the foamable resin particles, the composition of the base resin does not change, and the foaming agent does not affect the TH / THQ ratio. Therefore, the TH / TQ ratio of the foamable resin particles is the TH / TH / of the base resin. It can be said to be the TQ ratio. That is, the TH / TQ ratio obtained by analyzing the base resin which is the raw material of the foamable resin particles can be regarded as the TH / TQ ratio of the foamable resin particles. The conditions for GPC measurement of foamable resin particles using gel permeation chromatography will be described in detail in the following examples.

The TH / TQ ratio of the foamable resin particles may be less than 1.20, 1.19 or less, 1.18 or less, or 1.17 or less. , 1.16 or less, 1.15 or less, 1.14 or less, 1.13 or less, 1.12 or less. , 1.11 or less, 1.10 or less, or less than 1.10. The TH / TQ ratio of the foamable resin particles is low because the 10-hour half-life temperature is 74 ° C. or higher and 94 ° C. or lower in the copolymerization step (preparation step of the base resin) in the production of the foamable resin particles. This is a feature that appears when the initiator (X) is used. In other words, the foamable resin particles produced by using the polymerization initiator containing the polymerization initiator (X) having a 10-hour half-life temperature of 74 ° C. or higher and 94 ° C. or lower are TH / TQ within the above range. Can have a ratio. That is, the foamable resin particles produced by the production method described in the section <Method for producing foamable resin particles> described later may have a TH / TQ ratio within the above range. Further, among the polymerization initiators (X) described later, when benzoyl peroxide (also known as dibenzoyl peroxide), ditoluyl peroxide, toluyl benzoyl peroxide and the like are used as the polymerization initiator (X), the polymerization initiator Foamable resin particles having a lower TH / TQ ratio can be obtained as compared with the case where di-t-butylperoxyhexahydroterephthalate is used as (X). It can be said that the effervescent resin particles containing the base resin containing the acrylonitrile unit as the constituent unit and having a TH / TQ ratio of less than 1.20 tend to have a low VOC content. Further, it can be said that the effervescent resin particles containing the base resin containing the acrylonitrile unit as the constituent unit and having a TH / TQ ratio of less than 1.20 tend to be able to provide a molded product having a small amount of VOC emission. Further, the foamable resin particles having a TH / TQ ratio of less than 1.20 have an advantage that they are easily multiplied, that is, easily foamed.

The TH / TQ ratio of the foamable resin particles is preferably 0.90 or more, more preferably 1.00 or more. The foamable resin particles having a TH / TQ ratio of 0.90 or more have an advantage that a foamed molded product having excellent heat resistance can be provided.

In the production of foamable resin particles, the composition of the base resin does not change. Further, in the foamed particles produced by using the foamable resin particles, the structure of the foamable resin particles changes, but the composition of the foamable resin particles does not change. Further, in the foamed molded product produced by using the foamed particles produced by using the foamable resin particles, the structure of the foamed particles changes, but the composition of the foamed particles does not change. Therefore, the types of structural units, the content of each structural unit, and the weight average molecular weight obtained by analyzing the foamable resin particles, the foamed particles, or the foamed molded article are the base resin which is the raw material thereof. It can be regarded as the type of the structural unit contained in the above, the content of each structural unit, and the weight average molecular weight of the base resin. Further, the TH / TQ ratio obtained by analyzing the foamed particles or the foamed molded product can be regarded as the TH / TQ ratio of the foamable resin particles which are the raw materials thereof.

The weight average molecular weight of the foamable resin particles, the foamed particles, or the foamed molded product can be obtained by measuring the foamable resin particles, the foamed particles, or the foamed molded product by using gel permeation chromatography. The TH / TQ ratio of the base resin, the foamed particles, or the foamed molded product is determined by measuring the base resin, the foamed particles, or the foamed molded product by GPC using gel permeation chromatography to obtain a GPC measurement chart. It can be calculated by the same method as the TH / TQ ratio of the foamable resin particles.

<Manufacturing method of foamable resin particles>
The method for producing foamable resin particles according to an embodiment of the present invention includes a copolymerization step of copolymerizing a monomer containing a styrene monomer and an acrylonitrile monomer, and a foaming agent added to the obtained copolymer. The copolymerization step includes a continuous first polymerization step and a second polymerization step having different polymerization temperatures, including a foaming agent impregnation step of impregnating.

In the present specification, "a method for producing foamable resin particles according to an embodiment of the present invention" may be simply referred to as "the present production method". That is, the term "the present production method" is intended to be an embodiment of the method for producing foamable resin particles in the present invention. The "copolymer" in the present production method corresponds to the "base resin" contained in the foamable resin particles described in the section of <foamable resin particles>.

Hereinafter, each process related to this production method will be described, but the description in the section of <foamable resin particles> will be appropriately incorporated except for the matters described in detail below. Further, the present foamable resin particles, that is, the foamable resin particles described in the section of <Expandable resin particles> are preferably produced by the present production method, but may be produced by a method other than the present production method. .. That is, the method for producing the foamable resin particles is not limited to the mode of the present production method as described below.

The styrene monomer may contain a small amount of the ethylbenzene monomer used in the manufacturing process. The styrene monomer used in this production method is preferably as low as the content of ethylbenzene monomer in the styrene monomer, for example, preferably 130 ppm or less, more preferably 100 ppm or less, and 85 ppm. It is more preferably 70 ppm or less, and particularly preferably 70 ppm or less. By using a styrene monomer having a low ethylbenzene monomer content, the foamable resin particles obtained by this production method have an advantage that a foamed molded product having an even smaller amount of ethylbenzene emitted can be provided.

In the copolymerization step of this production method, the method of copolymerizing the monomer containing the styrene monomer and the acrylonitrile monomer is not particularly limited, and a conventionally known polymerization method can be used. As the copolymerization step, a suspension polymerization method in which polymerization is carried out in an aqueous suspension is preferable.

In the present specification, the "aqueous suspension" is a liquid (aqueous solution) in which resin particles, foamable resin particles and / or monomer droplets are dispersed in water or an aqueous solution using a stirrer or the like. Point to. Surfactants and monomers may be dissolved in the aqueous suspension, or water-insoluble dispersants, polymerization initiators, cross-linking agents, plasticizers, bubble conditioners, flame retardants, and A flame retardant aid or the like may be dispersed together with the monomer. The polymerization initiator, cross-linking agent, chain transfer agent and polymerization modifier used in the copolymerization step constitute a part of the obtained copolymer.

In the copolymerization step, the weight ratio of the resin and water in the aqueous suspension is 1.0 / 0.6 to 1.0 / 3.0 as the weight / water weight ratio of the obtained copolymer. It is preferable to have.

Dispersants that can be used in the copolymerization step include, for example, (a) poorly water-soluble inorganic salts such as tricalcium phosphate, magnesium pyrophosphate, hydroxyapatite, and kaolin, and (b) polyvinyl alcohol, methyl cellulose, polyacrylamide, and polyvinylpyrrolidone. Examples include water-soluble polymers such as. When a poorly water-soluble inorganic salt is used as the dispersant, an anionic surfactant such as α-olefin sulfonic acid sodium or dodecylbenzene sulfonic acid sodium is used in combination with the poorly water-soluble inorganic salt in order to increase dispersion stability. Is preferable. These dispersants may be further added to the aqueous suspension at any time during the copolymerization step, if desired.

The amount of dispersant used depends on the type of dispersant. When a poorly water-soluble inorganic salt is used as the dispersant, the amount of the dispersant used is preferably 0.1 part by weight or more and 1.5 parts by weight or less with respect to 100 parts by weight of water. When a water-soluble polymer is used as the dispersant, the dispersant is preferably used so as to be 30 ppm or more and 100 ppm or less in the aqueous suspension. When an anionic surfactant is used in combination with a poorly water-soluble inorganic salt, it is preferable to use the anionic surfactant so as to be 30 ppm or more and 100 ppm or less in the aqueous suspension.

In the copolymerization step in the present production method, a chain transfer agent and a polymerization modifier may be further used. Examples of the chain transfer agent include mercaptan compounds such as n-octyl mercaptan, n-dodecyl mercaptan, and t-dodecyl mercaptan. Examples of the polymerization modifier include α-methylstyrene dimer. Since α-methylstyrene dimer also contributes to the adjustment of the weight average molecular weight of the copolymer, it can be said to be a chain transfer agent. The chain transfer agent mainly functions to adjust the weight average molecular weight of the copolymer. The polymerization modifier mainly functions to regulate the polymerization rate.

In the copolymerization step, it is preferable to use α-methylstyrene dimer as a chain transfer agent. According to the above configuration, (a) the polymerization rate and the weight average molecular weight of the copolymer can be easily adjusted, and (b) odor is less likely to be generated from the foamed molded product that the foamable resin particles can provide.

The amount of the chain transfer agent and the polymerization modifier used is 0.6% by weight with respect to 100 parts by weight of the monomer because (a) the polymerization rate and (b) the weight average molecular weight of the copolymer can be easily adjusted. The amount is preferably 1 part or more, and more preferably 1.4 parts by weight or more.

As the polymerization initiator, it is desirable to mainly use the polymerization initiator (X) in the first polymerization step and mainly use the polymerization initiator (Y) in the second polymerization step.

The composition of the first polymerization step, such as the polymerization temperature and the polymerization time, is not particularly limited as long as the polymerization temperature is different from that of the second polymerization step. The polymerization temperature of the first polymerization step is, for example, 85 ° C. to 95 ° C., and the polymerization time of the first polymerization step is, for example, 4 hours to 7 hours.

The polymerization temperature in the first polymerization step is preferably 87 ° C. to 93 ° C., more preferably 88 ° C. to 92 ° C., and particularly preferably 89 ° C. to 91 ° C. According to this configuration, (a) foamable resin particles having D2230 / D1600 of 0.80 or more, that is, foamable resin particles having a small VOC content (emission amount) can be easily obtained. Further, according to the structure, the decomposition amount of the polymerization initiator (for example, the polymerization initiator (X)) can be adjusted in an optimum range. As a result, (a) the polymerization rate (reaction rate) can be easily adjusted, so that the polymerization stability is improved, and (b) foamable resin particles having an appropriate molecular weight range can be easily obtained.

The polymerization time of the first polymerization step is preferably 4.5 hours to 6.5 hours, and particularly preferably 5 hours to 6 hours. According to this configuration, there is an advantage that both productivity and polymerization stability can be achieved at the same time.

In the first polymerization step, it is preferable to use a polymerization initiator of the polymerization initiator (X) having a 10-hour half-life temperature of 74 ° C. or higher and 94 ° C. or lower.

In the first polymerization step, (a) a polymerization initiator (X) having a 10-hour half-life temperature of 74 ° C. or higher and 94 ° C. or lower is used, and (b) a polymerization reaction is carried out at a polymerization temperature of 85 ° C. or higher and 95 ° C. or lower. It is preferable to carry out. According to the above configuration, the polymerization reaction can be appropriately controlled.

Examples of the polymerization initiator (X) in the first polymerization step include organic peroxides such as benzoyl peroxide, lauroyl peroxide, di-t-butylperoxyhexahydroterephthalate, and (b) azobisisobutyronitrile. Examples thereof include azo compounds such as azobisdimethylvaleronitrile. As the polymerization initiator (X), it is particularly preferable to use benzoyl peroxide among these polymerization initiators because acrylonitrile, which can impart gas barrier properties, easily reacts.

As the above-mentioned polymerization initiator (X), one type may be used alone, or two or more types may be used in combination.

As the polymerization initiator (X), it is more preferable to use only the polymerization initiator having a 10-hour half-life temperature of 74 ° C. or higher and lower than 90 ° C. That is, in the first polymerization step, it is more preferable to use only the polymerization initiator (a) having a 10-hour half-life temperature of 74 ° C. or higher and lower than 90 ° C., and (b) (b) (b). -1) As the polymerization initiator (X), only a polymerization initiator having a 10-hour half-life temperature of 74 ° C. or higher and lower than 90 ° C. is used, and (b-2) at a polymerization temperature of 85 ° C. or higher and 95 ° C. or lower. It is more preferable to carry out a polymerization reaction. According to the above configuration, the polymerization initiator (X) used in the first polymerization step is mainly decomposed in the first polymerization step, so that the polymerization reaction can be controlled more appropriately.

In the first polymerization step, the polymerization initiator of the polymerization initiator (X) is used, and the amount of the polymerization initiator of the polymerization initiator (X) used is 0.08 weight by weight based on 100 parts by weight of the monomer. The amount is preferably 0.25 parts by weight or less, and more preferably 0.15 parts by weight or less. In the first polymerization step, when the amount of the polymerization initiator (X) used is 0.08 part by weight or more of (a) with respect to 100 parts by weight of the monomer, there is an advantage that the polymerization proceeds sufficiently. , (B) When it is 0.25 parts by weight or less, the polymerization reaction does not proceed rapidly, and the polymerization can be easily controlled. When the amount of the weight initiator (X) used is 0.15 parts by weight and 0.20 parts by weight or less, the weight average molecular weight of the obtained foamable resin particles is 170,000 or more and less than 200,000, and foaming of good quality. Sexual resin particles are obtained.

In this production method, the weight average molecular weight of the copolymer can be adjusted by variously combining the polymerization initiator, the chain transfer agent, and the polymerization conditions of the first polymerization step.

The second polymerization step is carried out continuously with the first polymerization at an arbitrary time point after the polymerization conversion rate of the monomer reaches 85%.

Here, the polymerization conversion rate of the monomer is calculated as follows:
Polymerization conversion of monomer (%) = (amount of monomer supplied to aqueous suspension-amount of monomer remaining in aqueous suspension) / simple supplied to aqueous suspension Dimer amount x 100
The above-mentioned "amount of monomer supplied to the aqueous suspension-amount of monomer remaining in the aqueous suspension" is, in other words, a single amount contained as a constituent unit in the copolymer. It can be said to be the amount of body. The "amount of monomer remaining in the aqueous suspension" is, for example, the residue (which may contain a monomer) obtained by filtering the aqueous suspension with a filter paper or the like. It can be measured by subjecting it to gas chromatography.

The polymerization temperature in the second polymerization step is different from the polymerization temperature in the first polymerization step, and the polymerization temperature in the second polymerization step is preferably 110 to 120 ° C. When the polymerization temperature in the second polymerization step is (a) less than 110 ° C., the VOC content (particularly the styrene content) in the obtained foamable resin particles cannot be reduced, and (b) when it exceeds 120 ° C. Since the internal pressure of the polymerization machine used in the polymerization step becomes high, high pressure resistance is required, and as a result, a heavy-equipped polymerization machine is required. The polymerization temperature of the second polymerization step is preferably higher than that of the first polymerization step. According to the above configuration, the VOC content in the obtained foamable resin particles can be reduced.

The polymerization time of the second polymerization step is preferably 3 to 13 hours, more preferably 4 to 11 hours, further preferably 5 to 9 hours, and particularly preferably 6 to 8 hours. When the polymerization time of the second polymerization step is (a) less than 3 hours, the VOC content (particularly the styrene content) in the obtained foamable resin particles cannot be reduced, and (b) when it exceeds 8 hours, Since the amount of decomposition of the flame-retardant aid (for example, dicumyl peroxide) is large, the effect of the flame-retardant aid is not sufficiently exhibited when the foamed molded product is burned, and as a result, the flame retardancy tends to deteriorate. ..

The polymerization temperature in the second polymerization step is preferably 111 ° C. to 119 ° C., more preferably 112 ° C. to 118 ° C., further preferably 113 ° C. to 117 ° C., and particularly preferably 114 ° C. to 116 ° C. According to this configuration, there is an advantage that VOC can be efficiently reduced below the upper limit of the internal pressure of the polymerizer of the polymerizer used.

The polymerization time of the second polymerization step is preferably 4 hours to 11 hours, more preferably 5 hours to 9 hours, and particularly preferably 6 hours to 8 hours. According to this configuration, there is an advantage that VOC can be reduced while maintaining quality such as flame retardancy.

In the second polymerization step, it is preferable to use a polymerization initiator (Y) having a 10-hour half-life temperature of 90 ° C. or higher and 100 ° C. or lower, and a polymerization initiator having a 10-hour half-life temperature of 90 ° C. or higher and 100 ° C. or lower. It is more preferable to mainly use (Y).

Examples of the polymerization initiator (Y) include t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-amylperoxyisopropyl monocarbonate, and t-amylperoxy-2-ethylhexyl monocarbonate. And 1,1-bis (t-butylperoxy) cyclohexane and the like. These polymerization initiators (Y) may be used alone or in combination of two or more. The polymerization initiator (Y) can be suitably used in the second polymerization step.

Note that 1,1-bis (t-butylperoxy) cyclohexane cleaves in two steps. The 10-hour half-life temperature when 1,1-bis (t-butylperoxy) cyclohexane before cleavage causes first-stage cleavage is 90 ° C. The 10-hour half-life temperature when the intermediate product produced after the first-stage cleavage causes the second-stage cleavage is about 5 ° C. higher than the 10-hour half-life temperature of the first stage, and is 95 ° C. or higher. Become. For 1,1-bis (t-butylperoxy) cyclohexane, the final product produced after the second stage cleavage acts mainly in the second polymerization step. Therefore, in the present specification, 1,1-bis (t-butylperoxy) cyclohexane is not regarded as a polymerization initiator (X) but as a polymerization initiator (Y).

In particular, t-butylperoxy-2-ethylhexyl monocarbonate and t-amylperoxy-2-ethylhexyl monocarbonate as the polymerization initiator (Y) remain in the foamable resin particles or in the aqueous suspension. It is preferable in that the reaction between the styrene and acrylonitrile is promoted.

The amount of the polymerization initiator (Y) used in the second polymerization step is preferably 0.25 parts by weight or more and 0.90 parts by weight or less, and 0.28 parts by weight or more and 0 by weight with respect to 100 parts by weight of the monomer. More preferably, it is .60 parts by weight or less. Within this range, styrene remaining in the foamable resin particles or the aqueous suspension tends to react easily with acrylonitrile, and the proportion of the styrene-acrylonitrile copolymer in the surface layer of the foamable resin particles tends to increase. ..

The second polymerization step may be performed in combination with the foaming agent impregnation step, that is, may be performed in the presence of a foaming agent.

The foaming agent impregnation step is started by adding the foaming agent to the aqueous suspension, and the specific treatment temperature (also referred to as impregnation temperature) and treatment time (also referred to as impregnation time) are not particularly limited.

There is an inverse relationship between the strength of the bonding force between the polymer chains in the base resin contained in the foamable resin particles and the efficiency of impregnation of the foaming agent into the copolymer in the production of the foamable resin particles. The present production method can provide foamable resin particles containing a base resin having a strong bonding force between polymer chains. Therefore, from the viewpoint of sufficiently impregnating the copolymer with the foaming agent, the impregnation temperature is preferably 110 ° C. to 120 ° C., more preferably 111 ° C. to 119 ° C., and 112 ° C. in the foaming agent impregnation step in the present production method. ° C. to 118 ° C. is more preferable, and 114 ° C. to 116 ° C. is particularly preferable. From the viewpoint of sufficiently impregnating the copolymer with the foaming agent, the impregnation time is preferably 3 hours to 13 hours, more preferably 4 hours to 11 hours, and 5 hours to 5 hours in the foaming agent impregnation step in the present production method. 9 hours is more preferred, and 6 to 8 hours is particularly preferred. When the second polymerization step is also performed as the foaming agent impregnation step, that is, when the second polymerization step and the foaming agent impregnation step are performed together, the polymerization temperature of the second polymerization step is the impregnation temperature of the foaming agent impregnation step. However, the polymerization time of the second polymerization step can be said to be the impregnation time of the foaming agent impregnation step.

It is preferable that the present production method further includes a drying step of drying the foamable resin particles. The foamable resin particles are obtained in a state of being dispersed in an aqueous suspension. Therefore, when the present production method includes a drying step, the obtained foamable resin particles can be suitably used for producing foamed particles and the like.

In the drying step, the method for drying the foamable resin particles is not particularly limited, and for example, a groove-type or cylindrical stirring dryer, a box-type or band-type aeration dryer, a fluidized bed dryer, or the like can be used. ..

The drying treatment in the drying step is preferably carried out at a temperature equal to or lower than the foaming temperature of the foamable resin particles, and more preferably carried out at 30 ° C. to 55 ° C. from the viewpoint of productivity. By adjusting the temperature at which the drying treatment is carried out (also referred to as the treatment temperature), the water content of the obtained foamable resin particles can be adjusted. When the drying treatment temperature in the drying step is (a) 30 ° C. or higher, the water content does not become too large, so that the foamed particles that the foamable resin particles can provide suppress the miniaturization of bubbles and reduce the VOC emission amount. When it can be reduced and (b) 55 ° C. or lower, the water content does not become too low, so that there is no possibility that the flame retardancy of the foamed molded product that the foamable resin particles can provide deteriorates.

The polymerization initiator (X) preferably contains at least benzoyl peroxide. That is, a more preferable aspect of the production method according to the embodiment of the present invention is a method for producing foamable resin particles, in which a monomer (polymer mixture) containing a styrene monomer and an acrylonitrile monomer is used. The copolymerization step includes a copolymerization step of copolymerizing and a foaming agent impregnation step of impregnating the obtained copolymer with a foaming agent, and the copolymerization step comprises a continuous first polymerization step and a second polymerization step having different polymerization temperatures. In the first polymerization step, a polymerization initiator (X) containing a polymerization initiator (X) having a 10-hour half-life temperature of 74 ° C. or higher and 94 ° C. or lower is used, and the polymerization initiator (X) is benzoyl peroxide. This is a method for producing a foamable resin particle, which comprises the above and has a TH / TQ ratio of the foamable resin particle of less than 1.20. According to this configuration, it is possible to provide an effervescent resin particle that can provide an effervescent molded article having a small amount of VOC emission, in other words, an effervescent molded article having high productivity.

The amount of benzoyl peroxide used in the first polymerization step is preferably 0.08 parts by weight or more and 0.25 parts by weight or less, and 0.15 parts by weight by weight of 0.20 parts by weight, based on 100 parts by weight of the monomer. The following is more preferable. According to this configuration, it is possible to provide a foamed molded product having a smaller VOC emission amount, in other words, a foamed resin particle capable of providing a foamed molded product having higher productivity.

<Effervescent molded product and its manufacturing method>
The foamable resin particles can be made into foamed particles by a general foaming method. Specific examples of the foaming method include a method in which the following (1) to (3) are sequentially performed: (1) foaming resin particles are placed in a container equipped with a stirrer, and (2) foaming is performed by a heat source such as steam. By heating the sex resin particles, (3) foaming is performed until a desired expansion ratio is reached, and foamed particles are obtained. In addition, the foamed particles may be referred to as pre-foamed particles, and therefore, the foaming method for obtaining the pre-foamed particles may be referred to as a pre-foamed method.

Foamed particles obtained by foaming foamable resin particles according to an embodiment of the present invention are also an embodiment of the present invention. The foamed particles according to the embodiment of the present invention can provide a foamed molded product having a small amount of VOC emissions, in other words, a foamed molded product having high productivity.

The foamed particles according to one embodiment of the present invention may have the following constitution. That is, the foamed particles according to another embodiment of the present invention are foamed particles obtained by foaming foamable resin particles, and the foamable resin particles have (a) styrene units and acrylonitrile units as constituent units. a base resin containing, (b) and a blowing agent, wherein the ratio of absorbance at a wavelength of 2230 cm ^-1 and a wavelength 1600 cm ^-1 in the infrared absorption spectrum of the surface of the expanded beads D2230 / D1600 is 0.80 or more.

The foamed particles according to one embodiment of the present invention may have the following constitution. That is, the foamed particles according to another embodiment of the present invention (a) contain styrene units and acrylonitrile units as constituent units, and (b) have a wavelength of 2230 cm- ¹ and a wavelength in the infrared absorption spectrum of the surface of the foamed particles. The absorbance ratio D2230 / D1600 at 1600 cm ^-1 is 0.80 or more.

The foamed particles can be made into a foamed molded product by molding by a general in-mold molding method. Specific examples of the in-mold molding method include a method in which foamed particles are filled in a mold that can be closed but cannot be sealed, and the foamed particles are heated and fused with steam to form a foamed molded product.

A foamed molded product obtained by in-mold molding of foamed particles according to an embodiment of the present invention is also an embodiment of the present invention. The foam molded product according to the embodiment of the present invention has an advantage that the amount of VOC emitted is small.

In the foam molded product according to the embodiment of the present invention, it is preferable that the amount of styrene released is 2 ppm or less and the amount of ethylbenzene released is less than 15 ppm. Here, the amount of styrene released and the amount of ethylbenzene released are the amounts released when a 0.025 g foam molded product is left in a container having a volume of 20 ml under the condition of 60 ° C. for 2 hours. Is. The amount of styrene and ethylbenzene released is shown as the concentration (ppm) in the gas in a container having a volume of 20 ml containing 0.025 g of the foamed molded product. The amount of styrene released in the foam molded product according to the embodiment of the present invention is preferably 1.5 ppm or less, more preferably 1.0 ppm or less, still more preferably 0.6 ppm or less, and particularly preferably. It is 0.5 ppm or less. The amount of ethylbenzene released in the foamed molded article according to the embodiment of the present invention is preferably less than 13 ppm, more preferably 10 ppm or less, still more preferably 7 ppm or less, and particularly preferably 5 ppm or less.

In the present specification, the terms "emission amount" and "emission amount" are synonymous and can be interchanged.

When the amount of styrene released and the amount of ethylbenzene released in the foamed molded product according to the embodiment of the present invention are within the above ranges, when the foamed molded product is used as an automobile interior material or a heat insulating material for building materials, sick house syndrome or the like It has the advantage that there is no risk of adversely affecting the body.

In the present specification, "the foamed molded product according to the embodiment of the present invention" may be simply referred to as "the present foamed molded product". That is, the term "present foam molded product" is intended to be an embodiment of the foam molded product in the present invention.

The oxygen index of the foamed molded product is preferably 26% or more, more preferably 27% or more, further preferably 28% or more, and particularly preferably 29% or more. According to the above configuration, when the foamed molded product is used as an automobile interior material or a heat insulating material for a building material, the foamed molded product has an advantage that it can exhibit sufficient flame retardant performance.

It is preferable that the foam molded product has excellent heat resistance. For example, when the foamed molded product is used as a heat insulating material or a material for a portion exposed to sunlight as an automobile member, it is preferable that the foamed molded product has little deformation when used at 90 ° C. or higher. Specifically, when a foamed molded product having a foaming ratio of 40 times is left to stand for 168 hours under the condition of 90 ° C., the dimensional change rate of the foamed molded product before and after leaving is preferably 0.4% or less. It is more preferably 35% or less, further preferably 0.3% or less, and particularly preferably 0.25% or less.

The average cell diameter of the surface layer of this foam molded product is preferably 50 μm or more and less than 100 μm, and more preferably 60 to 90 μm. When the average cell diameter is 50 μm or more, (a) the cell membrane has a sufficient thickness, so that the dimensional change of the foamed molded product with respect to temperature is small, and (b) the amount of VOC and total VOC emissions can be reduced. (C) Since the cell film has a sufficient thickness, the cell film is not melted by the pressurized steam during in-mold molding, and therefore the surface property of the foam molded product is improved. When the cell film is thin, the foamed molded product may swell in an environment of 90 ° C. or higher, and the dimensional stability of the foamed molded product may deteriorate. The expansion of the foamed molded product in a high temperature environment may be referred to as tertiary foaming. When the average cell diameter is less than 100 μm, the surface property of the foamed molded product is good.

In the present specification, the "average cell diameter of the surface layer" is the average chord length of the foamed particles existing on a straight line of the cut surface of the surface layer of the foamed molded product. The average chord length is a value obtained by measuring according to ASTM-D-2842-97 using a photograph obtained by projecting a cut surface of a foamed molded product. For the average chord length, 10 foam particles existing on a straight line of the cut surface of the surface layer of the foamed molded body are arbitrarily selected in the photograph obtained by projecting the cut surface of the foamed molded body, and the chord length of each of the foamed particles is selected. Measure and use the average value.

One embodiment of the present invention may have the following configuration.

(X1) A foamable resin particle containing a base resin containing a styrene unit and an acrylonitrile unit as a constituent unit and a foaming agent, and having a wavelength in the infrared absorption spectrum of the surface of the foamed particle in which the foamable resin particle is foamed. Foamable resin particles having an absorbance ratio D2230 / D1600 at 2230 cm ^-1 and a wavelength of 1600 cm ^-1 of 0.80 or more.

(X2) The foamable resin particles according to (X1), wherein the content of styrene in the foamable resin particles is less than 20 ppm, and the content of ethylbenzene is 130 ppm or less.

(X3) The foamable resin particles according to (X1) or (X2), wherein the weight average molecular weight is 150,000 or more and 220,000 or less.

(X4) In the base resin, (a) the content of the styrene unit is 55 parts by weight or more and 80 parts by weight or less, the content of the acrylonitrile unit is 20 parts by weight or more and 45 parts by weight or less, and ( b) The foamable resin particle according to any one of (X1) to (X3), wherein the total content of the styrene unit and the acrylonitrile unit is 100 parts by weight.

The foamable resin particles according to any one of (X1) to (X4), wherein the (X5) TH / TQ ratio is less than 1.20.

Foamed particles obtained by foaming the foamable resin particles according to any one of (X6), (X1) to (X5).

A foamed molded product obtained by in-mold molding of the foamed particles according to (X7) and (X6).

(X8) The foamed molded product according to (X7), wherein the average cell diameter of the surface layer is 50 μm or more and less than 100 μm.

(X9) The foamed molded product according to (X7) or (X8), wherein the emission amount of styrene is 2 ppm or less and the emission amount of ethylbenzene is less than 15 ppm.

(X10) A method for producing foamable resin particles, which is a copolymerization step of copolymerizing a monomer containing a styrene monomer and an acrylonitrile monomer, and foaming in which the obtained copolymer is impregnated with a foaming agent. The copolymerization step includes a continuous first polymerization step and a second polymerization step having different polymerization temperatures, and the first polymerization step has a 10-hour half-life temperature of 74 ° C. or higher and 94 ° C. or lower. A polymerization initiator (X) containing the above-mentioned polymerization initiator (X) is used, the polymerization initiator (X) contains benzoyl peroxide, and the TH / TQ ratio of the foamable resin particles is less than 1.20. A method for producing foamable resin particles, which is characterized by the above.

One embodiment of the present invention may have the following configuration.

(Y1) A foamable resin particle containing a base resin containing a styrene unit and an acrylonitrile unit as a constituent unit and a foaming agent, and having a wavelength in the infrared absorption spectrum of the surface of the foamed particle in which the foamable resin particle is foamed. Foamable resin particles having an absorbance ratio D2230 / D1600 of 0.8 or more at 2230 cm ^-1 and a wavelength of 1600 cm ^-1 .

(Y2) The foamable resin particles according to (Y1), wherein the content of styrene in the foamable resin particles is less than 20 ppm, and the content of ethylbenzene is 130 ppm or less.

(Y3) The foamable resin particles according to (Y1) or (Y2), wherein the weight average molecular weight is 150,000 or more and 220,000 or less.

Foamed particles obtained by foaming the foamable resin particles according to any one of (Y4), (Y1) to (Y3).

A foam molded product obtained by in-mold molding of the foam particles according to (Y5) and (Y4).

(Y6) The foamed molded product according to (Y5), wherein the average cell diameter of the surface layer is 50 μm or more and less than 100 μm.

(Y7) The foamed molded product according to (Y5) or (Y6), wherein the emission amount of styrene is 2 ppm or less and the emission amount of ethylbenzene is less than 15 ppm.

Examples and comparative examples are given below, but the present invention is not limited thereto.

The polymerization initiators, flame retardants, flame retardants and chain transfer agents used in Examples and Comparative Examples are as follows.
Polymerization initiator (X):
Benzoyl peroxide (Niper BW (manufactured by NOF Corporation)) (10-hour half-life temperature 74 ° C); and di-t-butylperoxyhexahydroterephthalate (Kayaester HTP-65W (manufactured by Kago Akzo Co., Ltd.)) (10-hour half-life temperature 83 ° C.);
Polymerization initiator (Y):
t-Butylperoxy-2-ethylhexyl monocarbonate (Perbutyl E (manufactured by NOF CORPORATION)) (10-hour half-life temperature 99 ° C.); and 1,1-bis (t-butylperoxy) cyclohexane (Perhexa C) (Manufactured by NOF CORPORATION)) (10-hour half-life temperature 90 ° C)
Flame retardants:
Tetrabromobisphenol A-bis (2,3-dibromo-2-methylpropyl) ether (Pyroguard SR-130 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)).
Flame Retardant:
Dikmil Peroxide (Park Mill D (manufactured by NOF CORPORATION)).
Chain transfer agent:
α-Methylstyrene dimer (MSD (manufactured by NOF CORPORATION)).
The molecular weight of the foamable resin particles in Examples and Comparative Examples, the content of styrene and ethylbenzene in the foamable resin particles, and the evaluation of the foamability of the foamable resin particles were measured by the following methods. In addition, "part" and "%" are based on weight unless otherwise specified, and "part by weight" and "%" are intended respectively.

(Weight average molecular weight measurement method)
0.02 g of foamable resin particles were dissolved in tetrahydrofuran 20 cc, and gel permeation chromatography (GPC) (HLC-8020 manufactured by Toso Co., Ltd., column: TSKgel Super HZM-H, column temperature: 40 ° C., flow rate: 0.35 ml The weight average molecular weight Mw was measured at / 1 min.). The weight average molecular weight was determined as a conversion value of standard polystyrene. The results obtained are shown in Tables 1 and 2 as "Mw (weight average molecular weight)".

(Method of calculating TH / TQ ratio of foamable resin particles)
0.02 g of the obtained foamable resin particles were dissolved in 20 ml of tetrahydrofuran (THF) to obtain a sample. Then, the obtained sample was subjected to GPC measurement under the following conditions using gel permeation chromatography to obtain a GPC measurement chart.
Measuring device: High-speed GPC device HLC-8220 manufactured by Tosoh Corporation
Columns used: Tosoh, 2 SuperHZM-H, 2 SuperH-RC, 4 in total Column temperature: 40 ° C
Mobile phase: THF (tetrahydrofuran)
Flow rate: 0.35 ml / min Injection amount: 10 μl
Detector: RI.

The TH / TQ ratio of the GPC curve of the obtained GPC measurement chart was determined by the method described above. The results obtained are shown in Tables 1 and 2 as "TH / TQ ratio".

(Method for measuring the content of styrene and ethylbenzene in foamed resin particles)
0.25 g of effervescent resin particles were dissolved in 20 cc of methylene chloride (with internal standard cyclopentanol), and gas chromatography GC-2014 manufactured by Shimadzu Corporation (capillary column: Rtx-1 manufactured by GL Science, column temperature condition: 50). After raising the temperature from ° C. to 80 ° C. (heating rate 3 ° C./min), raising the temperature from 80 ° C. to 180 ° C. (heating rate 10 ° C./min), carrier gas: helium) in the foamable resin particles. Styrene and ethylbenzene contained in the above were measured. The contents of styrene and ethylbenzene in the foamable resin particles were quantified from the obtained results using the measured calibration curves of styrene and ethylbenzene. The results obtained are shown in Tables 1 and 2 as "residual styrene monomer" and "ethylbenzene".

(Evaluation of foamability of foamable resin particles)
The foamable resin particles were placed in a steamer at 100 ° C. and heated for 5 minutes to obtain foamed particles. 10 g of the obtained foamed particles were placed in a 1000 cm ³ graduated cylinder, and the volume of the foamed particles (cm ³ ) was measured. The bulk ratio (cm ³ / g) was calculated by the following formula.

Bulk ratio (cm ³ / g) = Volume of foamed particles (cm ³ ) / 10 g
If the evaluation is less than 40 times, the bulk ratio does not increase to 40 times or more even if pre-foaming is performed by a pressure type pre-foaming machine, so this evaluation result is an index of foamability. The results obtained are shown in Tables 1 and 2 as "foaming (40x)".
〇 (Good): 50 times or more △ (Pass): 40 times or more × (Bad): Less than 40 times.

The manufacturing method of foamed particles is as follows.

(Manufacturing of foamed particles)
The foamable resin particles were sieved to separate the foamable resin particles having a particle diameter of 0.5 to 1.4 mm.

The separated effervescent resin particles are pre-foamed to a bulk magnification of 40 times under the condition of a blown vapor pressure of 0.09 to 0.10 MPa using a pressure type pre-foaming machine "Ohiraki Kogyo, BHP", and then pre-foamed. The foamed particles were left at room temperature for 1 day to obtain foamed particles having a bulk ratio of 40 times.

The blocking amount of the obtained foamed particles was measured by the following method.

(Measurement method of blocking amount at the time of preliminary foaming)
Blocking is a mass in which foamed particles are bonded to each other during a preliminary foaming operation. If the blocking amount is large, filling defects will occur in the molding process, so it is better that the blocking amount is small. The method for measuring the blocking amount is as follows.

The entire amount of foamed particles obtained by the foaming operation is passed through a wire mesh having a stitch spacing of 1 cm. The weight of the mass remaining on the wire net was measured, and the blocking amount was calculated by the following formula.
Blocking amount (%) = weight of mass / weight of total amount of foamed particles x 100
The blocking property was judged from the obtained blocking amount according to the following criteria. The results obtained are shown in Tables 1 and 2 as the "blocking amount".
〇 (Good): Less than 0.05% △ (Pass): Less than 0.01% 0.05% or more × (Defective): 0.1% or more.

<Measurement of absorbance ratio>
As for the absorbance ratio of the obtained foamable resin particles, 10 pre-foamed particles (foamed particles) were arbitrarily collected, and each of them was subjected to ATR on the surface of the pre-foamed particles (foaming ratio 40 times) under the following conditions. Infrared spectroscopic analysis (ATR-FTIR analysis) was performed to obtain an infrared absorption spectrum.
Equipment: Connect a single reflection type total reflection (ATR) measuring device [MIRacle] to FTIR [manufactured by Shimadzu Corporation, FTIR-8400S] ATR prism (high refractive index crystal species): zinc selenide (ZnSe)
Incident angle: 45 °
Measurement area: ^{4000cm -1} ~ 600cm -1
Detector: DLATGS
Depth of digging: 1.66
Number of reflections: 1 time Resolution: 4 cm ^-1
Number of integrations: 20 times Others: Processing not related to the measurement spectrum was performed with the infrared absorption spectrum measured without contact with the sample as the background.
In the ATR method, the intensity of the infrared absorption spectrum obtained by measurement changes depending on the degree of adhesion between the sample and the high-refractive index crystal, so that the absorbance at 1600 cm ^-1 is 0.05 to 0.10. The degree of adhesion of high refractive index crystals is adjusted for measurement.

Here, when measuring the surface of the pre-foamed particles, the particle surface was brought into close contact with the ATR prism as it was.

From the infrared absorption spectrum obtained as above, it was determined absorbance ratio between the absorbance of the absorbance and 2230 cm ^-1 of the 1600cm ^-1 (D2230 / D1600). In one embodiment of the invention, ATR-FTIR measurements are performed on the surface of any 10 prefoamed particles to exclude the minimum and maximum absorbance ratios. Then, the arithmetic mean of the absorbance ratios of the remaining eight pieces was taken as the absorbance ratio.

The preliminary foamed particles (foamed particles) used for measuring the absorptivity ratio were obtained by treating the foamable resin particles obtained in Examples and Comparative Examples described later in the order of (1) to (3) below. (1) The foamable resin particles were put into a pressurized foaming machine; (2) Next, steam was blown into the foaming machine at a blowing vapor pressure of 0.09 MPa to 0.10 MPa, and the pressure inside the foaming machine. Was prepared in the range of 0.01 MPa to 0.02 MPa to bring the temperature inside the foaming machine to 100 ° C. to 104 ° C., whereby the foamed particles were foamed at a magnification of 40 times; (3) Next, obtained. The foamed particles were cured at 25 ° C. for 12 to 24 hours to obtain foamed particles used for measuring the infrared absorption spectrum.

The manufacturing method of the foam molded product is as follows.

(Manufacturing of foam molding)
Pre-foamed particles with a bulk ratio of 40 times left at room temperature for 1 day are blown into the mold using a molding machine "Daisen, KR-57" at a vapor pressure of 0.05 MPa and a heating time of 22 seconds. A flat foam molded product having a thickness of 20 mm and a length of 400 mm and a width of 350 mm was obtained.

The obtained foamed molded product was evaluated for the amount of styrene and ethylbenzene emitted, the average cell diameter of the surface layer, the heat resistance, etc. by the following method.

(Measurement method of emission amount of styrene and ethylbenzene from foam molded product)
A sample piece was cut out from the foam molded product so as to weigh 0.025 g. The sample piece was placed in a pressure-resistant glass container having a volume of 20 ml and installed in Shimadzu HS-10 (connected to GC-2014). The storage condition of HS-10 was set to 60 ° C. × 2 hours, and styrene and ethylbenzene released at that time were collected. Shimadzu Gas Chromatography GC-2014 (capillary column: GL Science Rtx-1, column temperature condition: temperature rise from 50 ° C to 70 ° C (rise) by the same method as the method for measuring the styrene content in foamable resin particles. After the temperature temperature was 3 ° C./min), each substance collected was measured using a temperature rise from 70 ° C. to 180 ° C. (heating rate 10 ° C./min) and carrier gas: helium). Using the measured calibration curve of styrene and ethylbenzene, the amount of styrene and ethylbenzene emitted from the foam molded product was quantified from the obtained results. The amount of styrene and ethylbenzene emitted is shown as the concentration (ppm) in the gas in the pressure-resistant glass container containing the sample piece.

(Measurement of average cell diameter on the surface layer)
The average chord length of each foamed particle of the foamed molded product was measured according to ASTM-D-2842-97 using a photograph obtained by projecting a cut surface of the foamed molded product. Specifically, in a photograph of the cut surface of the foamed molded product, the average chord length was measured from the foamed particles existing on a straight line of the cut surface of the surface layer of the foamed molded product. Ten foamed particles existing on the surface layer of the foamed molded product were arbitrarily selected, and the average of the chord lengths of each of the foamed particles was used as the final value (average chord length). In the present specification, the average chord length thus obtained is defined as the average cell diameter of the surface layer of the foamed molded product.

(Heat resistance evaluation)
As described below, the heat resistance of the foamed molded product was evaluated by (a) calculating the dimensional change rate of the foamed molded product at 90 ° C. and (b) observing the swelling of the surface of the foamed molded product.

A foam molded product having a molded product magnification of 40 times was dried at 60 ° C. for 24 hours. Then, a sample piece having a length of 150, a width of 150, and a thickness of 20 (t) mm was cut out from the foam molded product. The initial dimension (D) was obtained by measuring the dimensions of the sample piece in the length direction and the width direction at three points each. Then, the foam molded product was left to stand in a dryer at 90 ° C. for 168 hours, and after being left to stand, the same measurement was performed to determine the dimension (E) after drying at 90 ° C. The dimensional change rate was calculated by the following formula, and the absolute value of the dimensional change rate was 0.4 or less, that is, the dimensional change rate −0.4% to 0.4% was regarded as acceptable.

When the dimensional change rate is a positive value, it indicates that the initial (before drying) dimension (D) is larger than the post-drying dimension (E), that is, the foamed molded product has shrunk. Further, when the dimensional change rate is a negative value, it indicates that the dimension (E) after drying is larger than the initial dimension (D), that is, it indicates that the foamed molded product has swelled.

Dimensional change rate (%) = ((D)-(E)) / (D) x 100
Absolute value of dimensional change rate is 0.4 or less: 〇 (good)
Absolute value of dimensional change rate is more than 0.4 and 0.5 or less: △ (pass)
Absolute value of dimensional change rate exceeds 0.5: × (defective)
(Examples 1 to 10, Comparative Examples 1 to 5)
110 parts by weight of water, 0.105 parts by weight of tricalcium phosphate, 0.0075 parts by weight of sodium α-olein sulfonate, and the amounts of polymerization initiator, chain transfer agent, and flame retardant shown in Table 1 in a 6 L autoclave with a stirrer. A flame retardant and a flame retardant aid were charged and deoxidized to a gauge pressure of −0.06 MPa with a vacuum pump.

Then, stirring of the raw materials by a stirrer was started, and the amounts of styrene monomer, alpha-methylstyrene monomer and acrylonitrile monomer shown in Table 1 were charged into the autoclave, and the raw materials were stirred for another 30 minutes. It was. Then, the first polymerization (first polymerization step) was carried out at the temperature (first polymerization temperature) and time (first polymerization time) shown in Table 1. Then, normal rich butane (normal butane weight part / isobutane weight part = 70/30) was charged into an autoclave of 5 parts by weight. Then, the second polymerization (second polymerization step) was carried out at the temperature (second polymerization temperature) and time (second polymerization temperature) shown in Table 1. Then, the temperature in the autoclave was cooled to 40 ° C., dehydrated, and further dried to obtain effervescent resin particles. The obtained foamable resin particles were subjected to various measurements and evaluations described above, and the results are shown in Tables 1 and 2.

The obtained foamable resin particles were pre-foamed by the above-mentioned method to obtain foamed particles, and then further molded in the mold by the above-mentioned method to obtain a 40-fold foamed molded product.

The obtained foamed particles and foamed molded product were subjected to the above-mentioned various measurements and evaluations. The results are shown in Tables 1 and 2.

According to one embodiment of the present invention, it is possible to provide foamable resin particles, pre-foamed particles (foamed particles), and a foamed molded product, which have a low VOC content and can suppress the emission amount of VOC. Therefore, one embodiment of the present invention can be suitably used in the fields of automobiles and building materials.

Claims (10)

1. Foamable resin particles containing a base resin containing a styrene unit and an acrylonitrile unit as a constituent unit and a foaming agent.
   Expandable resin particles, wherein the foaming ratio of absorbance at a wavelength of 2230 cm ^-1 and a wavelength 1600 cm ^-1 The resin particles in the infrared absorption spectrum of the foamed was foamed particle surface D2230 / D1600 is 0.80 or more ..
2. The foamable resin particles according to claim 1, wherein the content of styrene in the foamable resin particles is less than 20 ppm, and the content of ethylbenzene is 130 ppm or less.
3. The foamable resin particles according to claim 1 or 2, wherein the weight average molecular weight is 150,000 or more and 220,000 or less.
4. In the base resin, (a) the content of the styrene unit is 55 parts by weight or more and 80 parts by weight or less, the content of the acrylonitrile unit is 20 parts by weight or more and 45 parts by weight or less, and (b) the above. The effervescent resin particles according to any one of claims 1 to 3, wherein the total content of the styrene unit and the acrylonitrile unit is 100 parts by weight.
5. The foamable resin particles according to any one of claims 1 to 4, wherein the TH / TQ ratio is less than 1.20.
6. Foamed particles obtained by foaming the foamable resin particles according to any one of claims 1 to 5.
7. A foamed molded product obtained by molding the foamed particles according to claim 6 in a mold.
8. The foamed molded product according to claim 7, wherein the average cell diameter of the surface layer is 50 μm or more and less than 100 μm.
9. The foamed molded product according to claim 7 or 8, wherein the emission amount of styrene is 2 ppm or less and the emission amount of ethylbenzene is less than 15 ppm.
10. A method for producing foamable resin particles.
    A copolymerization step of copolymerizing a monomer containing a styrene monomer and an acrylonitrile monomer, and
    Including a foaming agent impregnation step of impregnating the obtained copolymer with a foaming agent.
    The copolymerization step includes a continuous first polymerization step and a second polymerization step having different polymerization temperatures.
    In the first polymerization step, a polymerization initiator containing a polymerization initiator (X) having a 10-hour half-life temperature of 74 ° C. or higher and 94 ° C. or lower is used.
    The polymerization initiator (X) contains benzoyl peroxide and contains.
    A method for producing foamable resin particles, wherein the TH / TQ ratio of the foamable resin particles is less than 1.20.

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