Recycled foamed polystyrene resin particles and a method for producing the same.

Abstract

This invention provides a method for producing recycled foamable polystyrene resin particles that can provide a recycled polystyrene foam molded article with excellent strength while using recycled materials as raw materials. [Solution] A method for producing recycled foamable polystyrene resin particles having a weight-average molecular weight of 250,000 (g / mol) or more, comprising a polymerization step of polymerizing styrene monomers onto a seed resin consisting of recycled polystyrene resin particles under predetermined conditions, and an impregnation step of impregnating the obtained polystyrene resin particles with a highly volatile foaming agent.

Description

Technical Field

[0001] The present invention relates to recycled expandable polystyrene resin particles and a method for producing the same.

Background Art

[0002] Polystyrene resin foamed molded articles obtained from expandable polystyrene resin particles have been widely used in applications such as food containers, cushioning materials, and heat insulating materials because of their excellent lightweight properties, heat insulating properties, strength, and hygiene.

[0003] On the other hand, in recent years, from the perspective of environmental considerations and the like, the recycling of plastic resources has been recognized as a social issue, and there is also a demand for the recycling of expandable polystyrene resin particles and polystyrene resin foamed molded articles (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, a foamed molded article formed by molding recycled expandable polystyrene resin particles made from a conventional recycled polystyrene resin (in other words, produced by recycling a polystyrene resin) tends to have a decrease in strength, and there has been room for improvement from this perspective.

[0006] In such a situation, an object of an embodiment of the present invention is to provide recycled expandable polystyrene resin particles that can provide a foamed molded article excellent in strength.

Means for Solving the Problems

[0007] The present inventors diligently studied to provide recycled foamable polystyrene resin particles capable of producing foamed molded articles with superior strength. As a result, they discovered that by setting the weight-average molecular weight of the recycled foamable polystyrene resin particles to 250,000 (g / mol) or more, it is possible to provide foamed molded articles with superior strength even when using recycled polystyrene resin as a raw material. Furthermore, they found that recycled foamable polystyrene resin particles with a weight-average molecular weight of 250,000 (g / mol) or more can be provided by a method comprising the steps of impregnating and polymerizing a styrene monomer into recycled polystyrene resin particles as a seed resin under predetermined conditions, and impregnating the polystyrene resin particles obtained in this step with a highly volatile foaming agent. Based on these findings, the present invention was completed.

[0008] In other words, one embodiment of the present invention includes the following configuration. [1] A method for producing recycled foamable polystyrene resin particles, comprising: a polymerization step of polymerizing styrene monomers onto recycled polystyrene resin particles as a seed resin; and an impregnation step of impregnating the polystyrene resin particles obtained in the polymerization step with a highly volatile foaming agent, wherein in the polymerization step, the amount of seed resin used is 50 parts by weight or more and the amount of styrene monomer used is 50 parts by weight or less out of a total of 100 parts by weight of the seed resin and the styrene monomer, and the polymerization step includes a step of increasing the weight-average molecular weight of the seed resin by 30,000 (g / mol) or more, resulting in a weight-average molecular weight of 250,000 (g / mol) or more. [2] The method for producing recycled foamed polystyrene resin particles according to [1], wherein the weight-average molecular weight of the recycled foamed polystyrene resin particles is 335,000 or less (g / mol). [3] A method for producing recycled foamable polystyrene resin particles according to [1] or [2], wherein in the polymerization step, the amount of polymerization initiator added when 1 / 3 of the total polymerization time has elapsed is 25% to 50% of the total amount of polymerization initiator added, and the amount of polymerization initiator added when 2 / 3 of the total polymerization time has elapsed is 50% to 95% of the total amount of polymerization initiator added. [4] The method for producing recycled foamable polystyrene resin particles according to any one of [1] to [3], wherein the seed resin contains 50 parts by weight or more of recycled polystyrene resin particles having a major axis of 0.9 to 1.2 mm and a minor axis of 0.6 to 0.9 mm in 100 parts by weight of the total amount of the seed resin. [5] The method for producing recycled foamable polystyrene resin particles according to any one of [1] to [4], wherein the total amount of polymerization initiator added in the polymerization step is 0.12 to 0.50 parts by weight per 100 parts by weight of the total amount of seed resin and styrene monomer used. [6] A method for producing recycled foamable polystyrene resin particles according to any one of [1] to [5], wherein the polymerization time in the polymerization step is 3.5 hours or less. [7] A method for producing recycled foamable polystyrene resin particles according to any one of [1] to [6], wherein in the polymerization step, a polymerization initiator having a half-life temperature of 90°C or higher for 10 hours is added in an amount of 0.01 to 0.30 parts by weight per 100 parts by weight of the total amount of the seed resin and the styrene monomer used. [8] The method for producing regenerated foamable polystyrene resin particles according to [7], wherein the polymerization initiator having a 10-hour half-life temperature of 90°C or higher is a polymerization initiator having a carbonate structure. [9] A method for producing recycled foamed polystyrene resin particles according to any one of [1] to [8], wherein the water content of the recycled foamed polystyrene resin particles is greater than 0.5%.

[10] A method for producing recycled foamable polystyrene resin particles according to any one of [1] to [9], wherein the residual styrene content of the recycled polystyrene resin particles is 200 ppm or more. A method for producing recycled polystyrene foam particles, comprising the step of foaming recycled foamable polystyrene resin particles produced by the manufacturing method described in any one of [1] to

[10] . A method for producing a recycled polystyrene foam molded article, comprising the step of molding recycled polystyrene foam particles produced by the manufacturing method described in

[12] and

[11] .

[13] Recycled foamable polystyrene resin particles having a weight-average molecular weight of 250,000 (g / mol) or more and a water content of more than 0.5%.

[14] Recycled foamable polystyrene resin particles as described in

[13] , having a weight-average molecular weight of 335,000 (g / mol) or less.

[15] Recycled foamable polystyrene resin particles as described in

[13] or

[14] , wherein the residual styrene content is 5000 ppm or less. A recycled polystyrene foam molded article, which is made by molding recycled polystyrene foam particles obtained by foaming recycled foamable polystyrene resin particles described in any one of

[16] ,

[13] to

[15] , and which has a bending strength of 0.30 MPa or more. [Effects of the Invention]

[0009] According to one embodiment of the present invention, recycled foamable polystyrene resin particles can be provided that can provide a foamed molded article with excellent strength. [Modes for carrying out the invention]

[0010] One embodiment of the present invention is described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Moreover, new technical features can be formed by combining the technical means disclosed in each embodiment. All academic and patent documents mentioned herein are incorporated herein by reference. Furthermore, unless otherwise specified herein, "A to B" representing a numerical range means "A or greater (including A and greater than A) and B or less (including B and less than B)."

[0011] In this specification, "X unit" in a polymer, copolymer, or resin means "a constituent unit derived from an X monomer." For example, "styrene-based unit" means "a constituent unit derived from a styrene-based monomer."

[0012] In this specification, "X-type resin" and "X-type polymer" refer to the resin and polymer, respectively, in which the X-type unit content is the highest among all constituent units of the resin and polymer.

[0013] [1. Method for producing recycled foamed polystyrene resin particles] A method for producing recycled foamable polystyrene resin particles according to one embodiment of the present invention includes a polymerization step of impregnating and polymerizing recycled polystyrene resin particles as a seed resin with styrene monomers, and an impregnation step of impregnating the polystyrene resin particles obtained in the polymerization step with a highly volatile foaming agent, wherein in the polymerization step, the amount of seed resin used is 50 parts by weight or more and the amount of styrene monomer used is 50 parts by weight or less out of a total amount of 100 parts by weight of the seed resin and the styrene monomers used, and the polymerization step includes a step of increasing the weight-average molecular weight of the seed resin by 30,000 (g / mol) or more, resulting in a method for producing recycled foamable polystyrene resin particles with a weight-average molecular weight of 250,000 (g / mol) or more.

[0014] According to this manufacturing method, recycled foamable polystyrene resin particles with a weight-average molecular weight of 250,000 (g / mol) or more can be provided using recycled polystyrene resin particles as a raw material. By foaming and molding these recycled foamable polystyrene resin particles, a recycled polystyrene foam molded article with excellent strength can be provided.

[0015] Furthermore, this manufacturing method uses recycled polystyrene resin particles directly as raw materials without converting them back to styrene monomers. Therefore, it is possible to provide recycled foamable polystyrene resin particles with a high recycling rate.

[0016] In this specification, the "method for producing recycled expandable polystyrene resin particles" may sometimes be simply referred to as the "production method", and the "method for producing expandable polystyrene resin particles according to an embodiment of the present invention" may sometimes be referred to as the "present production method". Also, in this specification, "recycled expandable polystyrene resin particles" may sometimes be referred to as "expandable resin particles", "recycled polystyrene-based expanded particles" may sometimes be referred to as "expanded particles", and "recycled polystyrene-based foam molded body" may sometimes be referred to as "foam molded body".

[0017] <1-1. Polymerization step> The polymerization step according to this production method will be described. The polymerization step is a step of polymerizing styrene monomers to the seed resin using recycled polystyrene resin particles as the seed resin. As described above, it can also be said that the polymerization step according to this production method is a step of polymerizing styrene monomers to the seed resin composed of recycled polystyrene resin particles. Therefore, the polymerization step can also be said to be a seed polymerization step.

[0018] (Polymerization operation) The polymerization operation carried out in the polymerization step will be described. The polymerization operation is an operation of polymerizing styrene monomers to the seed resin composed of recycled polystyrene resin particles. More specifically, the polymerization operation according to the polymerization step is an operation of adding styrene monomers and a polymerization initiator to the seed resin and polymerizing the seed resin and the styrene monomers for a predetermined time, and it can also be said to be an operation of increasing the molecular weight of the recycled polystyrene resin particles serving as the seed resin.

[0019] The polymerization operation in the polymerization step is not particularly limited as long as it can polymerize the seed resin and the styrene monomers to obtain recycled expandable polystyrene resin particles having a predetermined weight average molecular weight. However, the seed resin and optionally other components are dispersed in water as a dispersion medium to obtain an aqueous dispersion containing the seed resin and optionally other components. After heating the aqueous dispersion to a predetermined polymerization temperature, styrene monomers and a polymerization initiator are added to the aqueous dispersion, and a method of reacting the seed resin and the styrene monomers in the aqueous dispersion is preferably mentioned.

[0020] · Seed resin The seed resin used in the polymerization process will be described below. In the polymerization process, recycled polystyrene resin particles are used as the seed resin.

[0021] In this specification, "polystyrene resin particles" refers to resin particles containing polystyrene resin as the most abundant resin component, preferably 50% by weight or more of the total amount of resin components (100% by weight). Furthermore, "polystyrene resin" refers to a resin in which the content of styrene-derived constituent units (styrene units) is the most abundant among all constituent units of the resin.

[0022] More specifically, polystyrene resins include (i) homopolymers of styrene, and (ii) copolymers comprising styrene and other monomers polymerizable with styrene. Examples of other monomers polymerizable with styrene include styrene derivatives such as methylstyrene; polyfunctional vinyl compounds such as divinylbenzene; (meth)acrylic acid ester compounds such as methyl acrylate and methyl methacrylate; vinyl cyanide compounds such as (meth)acrylonitrile; diene compounds or derivatives thereof such as butadiene; unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; and N-alkyl-substituted maleimide compounds such as N-methylmaleimide.

[0023] In this specification, “recycled polystyrene resin particles” means polystyrene resin particles that contain polystyrene resin derived from recycled materials as a resin component. In this specification, “recycled materials” means (a) resin products that have been used and / or discarded after being in the form of resin products (e.g., foamed particles or foamed molded products, more specifically, food transport containers, casting scraps, food cushioning materials, etc.), and (b) waste generated during the manufacturing process of resin products. The recycled polystyrene resin particles according to this manufacturing method may be obtained by reshaping the above-mentioned recycled materials into particle form again through operations such as crushing, shredding, and melting.

[0024] The amount of polystyrene resin contained in the recycled polystyrene resin particles according to this manufacturing method is preferably 50% by weight or more, more preferably 60% by weight or more, more preferably 70% by weight or more, more preferably 80% by weight or more, more preferably 90% by weight or more, and particularly preferably 100% by weight or more, out of 100% by weight of the total amount of resin components. In other words, it is preferable that the recycled polystyrene resin particles according to this manufacturing method contain only polystyrene resin as the resin component. Furthermore, the polystyrene resin contained in the recycled polystyrene resin particles according to this manufacturing method may be entirely derived from recycled materials, or it may be a mixture of polystyrene resin derived from recycled materials and polystyrene resin derived from non-recycled materials.

[0025] The particle size of the recycled polystyrene resin particles used as the seed resin is not particularly limited, but it is preferable that the major axis is 0.9 to 1.2 mm and the minor axis is 0.6 to 0.9 mm, and more preferably that the major axis is 1.0 to 1.1 mm and the minor axis is 0.7 to 0.8 mm. By using recycled polystyrene resin particles having such particle sizes as the seed resin, adhesion between recycled polystyrene resin particles and between the resulting recycled foamed polystyrene resin particles can be suppressed.

[0026] Furthermore, in order to exhibit the anti-adhesion effect, it is not necessary for all of the seed resin recycled polystyrene resin particles to have the above particle size; it is sufficient if 50 parts by weight or more of the seed resin out of 100 parts by weight are recycled polystyrene resin particles having the above particle size.

[0027] In other words, from the viewpoint of suppressing adhesion between recycled polystyrene resin particles and between the resulting recycled foamed polystyrene resin particles, it is preferable that the seed resin in this manufacturing method contains 50 parts by weight or more of recycled polystyrene resin particles having a major axis of 0.9 to 1.2 mm and a minor axis of 0.6 to 0.9 mm, per 100 parts by weight of the total amount of seed resin.

[0028] Furthermore, from the viewpoint of obtaining a higher anti-adhesion effect, it is preferable that the proportion of recycled polystyrene resin particles having the above particle size in the seed resin is higher. Therefore, the proportion of recycled polystyrene resin particles having the above particle size in 100 parts by weight of the total amount of seed resin is more preferably 60 parts by weight or more, more preferably 70 parts by weight or more, more preferably 80 parts by weight or more, more preferably 90 parts by weight or more, and may be 100 parts by weight (i.e., the total amount).

[0029] The residual styrene content of the recycled polystyrene resin particles, which serve as the seed resin, is not particularly limited, but is preferably 200 ppm or more, more preferably 500 ppm or more, and even more preferably 800 ppm or more. Furthermore, the upper limit of the residual styrene content is not particularly limited, but may be, for example, 3000 ppm or less. The residual styrene content of the recycled polystyrene resin particles is measured by the method described in the examples.

[0030] The weight-average molecular weight of the recycled polystyrene resin particles used as the seed resin is not particularly limited, but is preferably 180,000 (mol / g) or more, and more preferably 185,000 (mol / g) or more. By using recycled polystyrene resin particles having such a weight-average molecular weight as the seed resin, it is possible to provide recycled foamable polystyrene resin particles that can provide foamed molded articles with higher strength, and it is also possible to provide recycled foamable polystyrene resin particles with a desired weight-average molecular weight in a shorter time. Furthermore, the upper limit of the weight-average molecular weight of the recycled polystyrene resin particles is not particularly limited, but may be, for example, 270,000 (mol / g) or less. The weight-average molecular weight of the recycled polystyrene resin particles is measured by the method described in the examples.

[0031] • Sterile monomer The styrene monomer used in the polymerization process is as described in the "Type of Resin" section above.

[0032] In the polymerization process, the amount of seed resin used is 50 parts by weight or more out of 100 parts by weight of the total amount of seed resin and styrene monomer used, and the amount of styrene monomer used in the polymerization process is 50 parts by weight or less out of 100 parts by weight of the total amount of seed resin and styrene monomer used. By setting the amounts of seed resin and styrene monomer used within the above ranges, a foamed molded article with excellent strength can be provided.

[0033] The amount of seed resin used in the polymerization process is not particularly limited as long as it is within the above range, but it may be 50 to 80 parts by weight or 50 to 70 parts by weight out of 100 parts by weight of the total amount of seed resin and styrene monomer used. Similarly, the amount of styrene monomer used in the polymerization process is not particularly limited as long as it is within the above range, and may be 20 to 50 parts by weight or 30 to 50 parts by weight out of 100 parts by weight of the total amount of seed resin and styrene monomer used.

[0034] In the polymerization process, it is not necessary to add (react with) the entire amount of styrene monomer at once; it may be added in stages according to the progress of the polymerization reaction. In this case, the amount of styrene monomer used in the polymerization process refers to the total amount of styrene monomer used (added) during the polymerization operation.

[0035] In the polymerization process, when styrene monomers are added in stages, it is preferable, for example, to add styrene monomers so that the amount of styrene monomers added when 1 / 3 of the total polymerization time has elapsed is 25% to 35% of the total amount of styrene monomers added, and the amount of styrene monomers added when 2 / 3 of the total polymerization time has elapsed is 50% to 75% of the total amount of styrene monomers added.

[0036] • Polymerization initiator The polymerization initiator used in the polymerization process is not particularly limited, but examples include polymerization initiators with a 10-hour half-life temperature of 50°C or higher and less than 90°C, such as benzoyl peroxide, lauroyl peroxide, ditoluyl peroxide, toluylbenzoyl peroxide, t-butyl peroxy-2-ethylhexanoate, t-butyl perpivalate, di-t-butyl peroxyhexahydroterephthalate; and / or t-butyl peroxybenzoate, isopropyl-t-butyl peroxycarbonate, t-butyl peroxyisopropyl carbonate, 1,1-di(t-butylperoxy)-3,3, Polymerization initiators with a 10-hour half-life temperature of 90°C or higher, such as 5-trimethylcyclohexane, 1,1-di(t-amylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 1,1-di-t-butylperoxy-2,4-di-t-butylcyclohexane, t-butylperoxy-2-ethylhexyl carbonate (also called t-butylperoxy-2-ethylhexyl monocarbonate), and t-amylperoxy-2-ethylhexyl carbonate (also called t-amylperoxy-2-ethylhexyl monocarbonate), can be used. Furthermore, one of these compounds may be used alone as the polymerization initiator, or two or more may be used in combination.

[0037] Among the polymerization initiators mentioned above, it is preferable to use a polymerization initiator with a 10-hour half-life temperature of 90°C or higher, as this can reduce the amount of residual styrene and provide recycled foamable polystyrene resin particles with a low concentration of volatile organic compounds (VOCs). It is also preferable to use a polymerization initiator that has a 10-hour half-life temperature of 90°C or higher and has a carbonate structure. Examples of such polymerization initiators having a carbonate structure include t-butyl peroxy-2-ethylhexyl monocarbonate and t-amyl peroxy-2-ethylhexyl monocarbonate. That is, in one embodiment of the present invention, it is preferable that the polymerization initiator having a carbonate structure is one or more selected from t-butyl peroxy-2-ethylhexyl monocarbonate and t-amyl peroxy-2-ethylhexyl monocarbonate.

[0038] Furthermore, in order to achieve the effect of reducing residual styrene content, it is not necessary for all of the added polymerization initiators to be polymerization initiators with a 10-hour half-life temperature of 90°C or higher. If 0.01 to 0.25 parts by weight of a polymerization initiator having a carbonate structure are added per 100 parts by weight of the total amount of seed resin and styrene monomer used, the remainder may be other polymerization initiators, for example, polymerization initiators with a 10-hour half-life temperature of 50°C or higher and less than 90°C.

[0039] When using a polymerization initiator with a 10-hour half-life temperature of 90°C or higher and a polymerization initiator with a 10-hour half-life temperature of 50°C or higher and less than 90°C in combination, the amount of the polymerization initiator with a 10-hour half-life temperature of 90°C or higher used is not particularly limited as long as it is between 0.01 and 0.25 parts by weight per 100 parts by weight of the total amount of seed resin and styrene monomer used, but is preferably 0.03 to 0.20 parts by weight, and more preferably 0.05 to 0.10 parts by weight. Furthermore, the amount of the polymerization initiator with a 10-hour half-life temperature of 50°C or higher and less than 90°C used is preferably 0.11 to 0.25 parts by weight, more preferably 0.13 to 0.22 parts by weight, and even more preferably 0.15 to 0.20 parts by weight per 100 parts by weight of the total amount of seed resin and styrene monomer used.

[0040] In other words, in one embodiment of the present invention, it is preferable to add 0.01 to 0.25 parts by weight of a polymerization initiator having a 10-hour half-life temperature of 90°C or higher, per 100 parts by weight of the total amount of seed resin and styrene monomer used. Furthermore, it is more preferable to add a polymerization initiator having a 10-hour half-life temperature of 50°C or higher and less than 90°C, such that the total amount added with the polymerization initiator having a 10-hour half-life temperature of 90°C or higher is 0.12 to 0.50 parts by weight.

[0041] The total amount of polymerization initiator added in the polymerization process is not particularly limited, but is preferably 0.12 to 0.50 parts by weight, more preferably 0.15 to 0.45 parts by weight, and even more preferably 0.18 to 0.40 parts by weight, per 100 parts by weight of the total amount of seed resin and styrene monomer used. By using the polymerization initiator within this range, the polymerization reaction can be carried out efficiently, and the production cycle of recycled foamed polystyrene resin particles using this manufacturing method can be shortened. In addition, the amount of residual styrene (VOC component) in the recycled foamed polystyrene resin particles can be reduced. Note that in the polymerization process, it is not necessary to add the entire amount of polymerization initiator to be used at once, but it may be added in stages according to the progress of the polymerization reaction. In this case, the amount of polymerization initiator used in the polymerization process refers to the total amount of polymerization initiator used.

[0042] In the polymerization process, when the polymerization initiator is added in stages, it is preferable to add the polymerization initiator so that the amount added when 1 / 3 of the total polymerization time has elapsed is 25% to 50% of the total amount added, and the amount added when 2 / 3 of the total polymerization time has elapsed is 50% to 95% of the total amount added. Then, it is preferable to add the remaining polymerization initiator during the remaining 1 / 3 of the polymerization time. By adding the polymerization initiator in stages as described above, the gel effect can be more easily exhibited compared to when the total amount of polymerization initiator is added all at once (non-staged addition). In other words, the polymerization termination reaction can be suppressed and the progress of the polymerization growth reaction can be promoted, so the molecular weight of the seed resin can be efficiently improved, and as a result it becomes possible to efficiently provide recycled foamable polystyrene resin particles with a relatively large weight-average molecular weight of 250,000 (g / mol) or more. Furthermore, by adding a relatively small amount of polymerization initiator (5% to 45% of the total amount added) particularly in the latter half of polymerization (after 2 / 3 of the total polymerization time has elapsed), the amount of polymerization initiator relative to the styrene monomer in the reaction system can be reduced, that is, the reaction initiation point can be reduced, making it possible to provide recycled foamable polystyrene resin particles with a higher weight-average molecular weight.

[0043] In the polymerization process, it is particularly preferable to use in combination a polymerization initiator with a 10-hour half-life temperature of 90°C or higher and a polymerization initiator with a 10-hour half-life temperature of 50°C or higher but less than 90°C, and to add them in stages. In this case, it is preferable to add only a relatively large amount (for example, about 50-95% of the total amount used) of the polymerization initiator with a 10-hour half-life temperature of 50°C or higher but less than 90°C in the first half of polymerization (from the start of polymerization until 2 / 3 of the total polymerization time has elapsed), and then add the remainder of the polymerization initiator with a 10-hour half-life temperature of 50°C or higher but less than 90°C and the polymerization initiator with a 10-hour half-life temperature of 90°C or higher in the second half of polymerization (after 2 / 3 of the total polymerization time has elapsed). By adding polymerization initiators with a 10-hour half-life temperature of 90°C or higher and polymerization initiators with a 10-hour half-life temperature of 50°C or higher but less than 90°C in a stepwise manner as described above, it is possible to more efficiently improve the weight-average molecular weight of the seed resin while more efficiently reducing the amount of residual styrene (VOC component) in the recycled foamed polystyrene resin particles.

[0044] From the viewpoint of more efficiently improving the weight-average molecular weight of the seed resin while more efficiently reducing the amount of residual styrene (VOC component) in the recycled foamed polystyrene resin particles, in the polymerization process according to a preferred embodiment of the present invention, from the start of polymerization until 1 / 3 of the total polymerization time has elapsed, only polymerization initiators with a 10-hour half-life temperature of 50°C or higher and less than 90°C are added, such that the amount of polymerization initiators added with a 10-hour half-life temperature of 50°C or higher and less than 90°C is 25% to 50% of the total amount of polymerization initiators added. From the point when 1 / 3 of the total polymerization time has elapsed until 2 / 3 of the total polymerization time has elapsed, it is preferable to add only polymerization initiators with a 10-hour half-life temperature of 50°C or higher and less than 90°C, so that the total amount of polymerization initiators with a 10-hour half-life temperature of 50°C or higher and less than 90°C is 50% to 95% of the total amount of polymerization initiators added. After 2 / 3 of the total polymerization time has elapsed, it is preferable to add the remaining polymerization initiators with a 10-hour half-life temperature of 50°C or higher and polymerization initiators with a 10-hour half-life temperature of 90°C or higher.

[0045] ·water In the polymerization process, the water that can be used as a dispersion medium is not particularly limited, but pure water such as RO water (water purified by reverse osmosis), deionized water (water purified by ion exchange resin), and distilled water (distilled water) can be suitably used.

[0046] Other ingredients Other components that can be used in the polymerization process include, for example, dispersants and surfactants.

[0047] In the polymerization process, it is preferable to further use a dispersant in addition to the seed resin, styrene monomer, and polymerization initiator. The use of a dispersant can improve the dispersibility of the seed resin and styrene monomer and suppress adhesion.

[0048] The dispersants that can be used in the polymerization process are not particularly limited and include organic dispersants (e.g., water-soluble polymers) and inorganic dispersants (e.g., poorly water-soluble inorganic salts and water-soluble inorganic salts).

[0049] Examples of water-soluble polymers that can be used as organic dispersants include polyvinyl alcohol, partially saponified polyvinyl alcohol, polyacrylates, polyacrylamide, polyvinylpyrrolidone, carboxymethylcellulose, and methylcellulose.

[0050] Examples of poorly water-soluble inorganic salts that can be used as inorganic dispersants include kaolin, calcium pyrophosphate, calcium phosphate (e.g., tricalcium phosphate), calcium carbonate, magnesium pyrophosphate, magnesium phosphate, magnesium carbonate, and magnesium oxide.

[0051] Examples of water-soluble inorganic salts that can be used as inorganic dispersants include sodium nitrite, sodium chloride, potassium chloride, sodium sulfate, sodium bisulfite, potassium bisulfite, and ammonium bisulfite.

[0052] These dispersants may be used individually or in combination of two or more.

[0053] In the polymerization process, it is preferable to further use a surfactant in addition to the seed resin and styrene monomer. The use of a surfactant has the advantage of suppressing mutual adhesion.

[0054] While there are no particular limitations on the surfactants that can be used in the polymerization process, anionic surfactants are preferred. More specifically, examples of such anionic surfactants include sodium alkyldiphenyl ether sulfonate, sodium α-olefin sulfonate, and sodium dodecylbenzene sulfonate. These surfactants may be used individually or in combination of two or more.

[0055] Examples of crosslinking agents that can be used in the polymerization process are not particularly limited, but include divinylbenzene (DVB), m-diisopropenylbenzene, and ethylene glycol diacrylate.

[0056] The amount of crosslinking agent added in the polymerization process is not particularly limited, but is preferably 0.005 to 0.02 parts by weight, more preferably 0.008 to 0.018 parts by weight, and even more preferably 0.010 to 0.015 parts by weight, per 100 parts by weight of the total amount of seed resin and styrene monomer used. By adding the crosslinking agent within the above range, the surface elongation of the resulting foamed molded article can be improved, and melting can be suppressed.

[0057] Chain transfer agents that can be used in the polymerization process are not particularly limited, but include mercaptan compounds such as n-octyl mercaptan, n-dodecyl mercaptan, and t-dodecyl mercaptan.

[0058] In the polymerization process, other additives besides those exemplified may be used, as long as they do not inhibit the polymerization reaction.

[0059] The amount of other components added in the polymerization process is not particularly limited and can be appropriately determined by a person skilled in the art as long as it does not inhibit the polymerization reaction. Furthermore, the timing of adding other components is not particularly limited and may be before the start of the polymerization reaction, during the process of polymerization, or after the completion of the polymerization reaction.

[0060] • Polymerization conditions In the polymerization process, it is preferable to increase the weight-average molecular weight of the seed resin by 30,000 g / mol or more. In other words, in the polymerization process, it is preferable to polymerize styrene monomers into the seed resin so that the weight-average molecular weight of the seed resin increases by 30,000 g / mol or more. In the polymerization process, the extent to which the weight-average molecular weight of the seed resin is increased is not particularly limited as long as it is 30,000 g / mol or more, but it may be 50,000 g / mol or more, or 70,000 g / mol or more. Furthermore, there is no particular upper limit to the extent to which the weight-average molecular weight of the seed resin is increased, and for example, it may be 150,000 or less. The extent to which the weight-average molecular weight of the seed resin is increased in the polymerization process can be controlled by adjusting the amount and timing of addition of styrene monomers, the type, amount and timing of addition of polymerization initiators, polymerization temperature, polymerization time, etc.

[0061] In the polymerization process, the polymerization temperature is not particularly limited as long as it increases the weight-average molecular weight of the seed resin by 30,000 (g / mol) or more, but is preferably 82°C to 102°C, more preferably 87°C to 97°C, and even more preferably 90°C to 95°C. By setting the polymerization temperature within this range, the polymerization reaction can proceed while exhibiting a gel effect, which has the advantage of efficiently increasing the weight-average molecular weight of the seed resin (in other words, it is possible to efficiently provide recycled foamable polystyrene resin particles with a weight-average molecular weight of 250,000 or more). The polymerization temperature can also be said to be the temperature of the water dispersion containing the seed resin when adding the styrene monomer and polymerization initiator.

[0062] In the polymerization process, the time for polymerization of the seed resin and the styrene monomer (polymerization time) is not particularly limited as long as the weight-average molecular weight of the seed resin is increased to 30,000 (g / mol) or more, but it is preferably within 3.5 hours, and more preferably within 3.0 hours. The lower limit of the polymerization time is also not particularly limited and may be, for example, 1.0 hour or more. This manufacturing method, by using recycled polystyrene resin particles, in particular recycled polystyrene resin particles having a predetermined particle size, as the seed resin, and / or by adding polymerization initiators in stages, makes it possible to complete the polymerization reaction in a shorter time compared to a normal seed polymerization system, that is, efficient polymerization is possible.

[0063] The polymerization process is preferably carried out in a container that is airtight and has pressure and heat resistance. By using such a container, the polymerization process and the foaming agent impregnation process described later can be carried out continuously in a single container, reducing the time and cost required for transportation. A suitable container for this purpose is, for example, an autoclave equipped with a stirrer.

[0064] ·Holding process This manufacturing method may include a holding step in which the system after the polymerization step is maintained at the polymerization temperature. In the holding step, the time for maintaining the system after the polymerization step at the polymerization temperature is not particularly limited, but it may be, for example, 10 minutes to 1 hour.

[0065] <1-2. Impregnation process> This manufacturing method includes an impregnation step in which a highly volatile foaming agent is impregnated into the polystyrene resin particles obtained in the polymerization step. The impregnation step can also be described as a step in which foaming properties are impregnated into the polystyrene resin particles obtained in the polymerization step by impregnating them with a highly volatile foaming agent, thereby obtaining regenerated foamable polystyrene resin particles.

[0066] Examples of highly volatile blowing agents used in the impregnation process include propane, isobutane, n-butane, isopentane, n-pentane, and neopentane. One of these compounds may be used alone as the highly volatile blowing agent, or two or more may be used in combination. The highly volatile blowing agent is preferably (i) a mixture of isobutane and n-butane, and / or (ii) a mixture of isopentane and n-pentane, and optionally neopentane, and in particular, a mixture of isobutane and n-butane with a high content of n-butane, known as normal-rich butane, is preferred.

[0067] The amount of foaming agent used in the impregnation process is not particularly limited, but is preferably 4.0 to 10.0 parts by weight, more preferably 5.0 to 9.0 parts by weight, and even more preferably 6.0 to 8.0 parts by weight, based on 100 parts by weight of the total amount of seed resin and styrene monomer used.

[0068] In the impregnation process, an organic solvent may be used to adjust the foaming rate. Examples of organic solvents include cyclohexane and aromatic hydrocarbons (e.g., toluene, xylene, and ethylbenzene).

[0069] The amount of organic solvent used in the impregnation process is not particularly limited, but from the viewpoint of suppressing melting of the resulting foamed molded product, it is preferably 0.1 to 3.0 parts by weight per 100 parts by weight of the total amount of seed resin and styrene monomer used.

[0070] In the impregnation process, from the viewpoint of efficiently impregnating the polystyrene resin particles with the highly volatile foaming agent, it is preferable to impregnate the polystyrene resin particles with the highly volatile foaming agent while they are heated. From the above viewpoint, it is preferable that the temperature at which the polystyrene resin particles are heated in the impregnation process is 110°C or higher.

[0071] <1-3. Recycled foamed polystyrene resin particles> This section describes the recycled foamed polystyrene resin particles produced by this manufacturing method. Because the foamed polystyrene resin particles produced by this manufacturing method are manufactured using this method, it is possible to provide recycled polystyrene foam molded articles with excellent strength, even though recycled polystyrene resin particles are used as raw materials, that is, even though recycled materials are used as raw materials.

[0072] The weight-average molecular weight (Mw) of the recycled foamed polystyrene resin particles produced by this manufacturing method is 250,000 (g / mol) or more. Because the recycled foamed polystyrene resin particles produced by this manufacturing method have a relatively high weight-average molecular weight of 250,000 (g / mol) or more, it is possible to provide recycled polystyrene foam molded articles with excellent strength. There is no particular upper limit to the weight-average molecular weight of the recycled foamed polystyrene resin particles produced by this manufacturing method, but it is preferable that it be 335,000 (g / mol) or less in order to provide recycled polystyrene foam molded articles with excellent surface elongation. In other words, from the viewpoint of providing recycled polystyrene foam molded articles with excellent strength and surface elongation, it is particularly preferable that the weight-average molecular weight of the recycled foamed polystyrene resin particles produced by this manufacturing method is between 250,000 (g / mol) and 335,000 (g / mol). The moisture content of the recycled foamed polystyrene resin particles produced by this manufacturing method is over 0.5%. Virgin foamed polystyrene resin particles (those not made from recycled materials) typically have a moisture content of 0.5% or less, and when salt is used in the polymerization process, the moisture content becomes even lower due to osmotic pressure, falling to less than 0.1%. Therefore, unless moisture has been intentionally added, a moisture content of foamed polystyrene resin particles exceeding 0.5% indicates that these foamed polystyrene resin particles are recycled foamed polystyrene resin particles manufactured using recycled materials.

[0073] For foamed polystyrene resin particles, having a weight-average molecular weight of 250,000 (g / mol) or more and a water content of more than 0.5% means that the foamed polystyrene resin particles are recycled foamed polystyrene resin particles produced by the present manufacturing method. That is, in one embodiment of the present invention, recycled foamed polystyrene resin particles having a weight-average molecular weight of 250,000 (g / mol) or more and a water content of more than 0.5% are provided, and recycled foamed polystyrene resin particles having such a configuration according to one embodiment of the present invention are referred to as these recycled foamed polystyrene resin particles. The weight-average molecular weight and water content of the recycled foamed polystyrene resin particles are values ​​measured by the method described in the examples.

[0074] The water content of these recycled foamed polystyrene resin particles is not particularly limited as long as it is greater than 0.5%, and may be, for example, 0.6% or more, or 0.7% or more. Furthermore, since it is possible to provide recycled polystyrene foamed particles with a cell diameter (average chord length) of 40 to 150 μm that are non-sticky, maintain high strength, suppress melting, and have excellent surface elongation, it is preferable that the water content be 1.0% or less, and more preferably 0.9% or less.

[0075] The residual styrene content of the recycled foamed polystyrene resin particles is not particularly limited, but from the viewpoint of reducing harmful substances, it is preferably 5000 ppm or less, more preferably 3000 ppm or less, and even more preferably 1000 ppm or less. If the residual styrene content of the recycled foamed polystyrene resin particles is within the above range, the amount of styrene components released from the foamed molded article can be sufficiently reduced. Furthermore, the lower limit of the residual styrene content is not particularly limited, but for example, it is 50 ppm or more. The residual styrene content of the recycled foamed polystyrene resin particles is measured by the method described in the examples.

[0076] The recycled foamed polystyrene resin particles may further contain external additives on their surface. Examples of such external additives include anti-blocking agents (e.g., zinc stearate and magnesium stearate, which are metal salts of higher fatty acids), fusion accelerators (e.g., castor wax (hydroxystearate triglyceride), sorbitan stearate, triesters, diesters, monoesters, sucrose esters, etc., of higher fatty acids), antistatic agents, and water repellents. The manufacturing method may further include a step of adding (coating) these external additives to the obtained recycled foamed polystyrene resin particles.

[0077] [2. Recycled polystyrene foam particles] <2-1. Recycled polystyrene foam particles> In one embodiment of the present invention, recycled foamed polystyrene resin particles are provided, which are obtained by foaming recycled foamed polystyrene resin particles (i.e., the recycled foamed polystyrene resin particles) produced by the present manufacturing method.

[0078] The recycled polystyrene foam particles according to one embodiment of the present invention (hereinafter sometimes referred to as "the recycled polystyrene foam particles") have the above-described structure, and therefore, even though recycled polystyrene resin particles are used as raw materials, that is, even though recycled materials are used as raw materials, it is possible to provide a recycled polystyrene foam molded article with excellent strength.

[0079] The cell diameter (average chord length) of the recycled polystyrene foam particles is not particularly limited, but since melting is suppressed and a foam molded article with excellent strength and surface elongation can be provided, the cell diameter of the foam particles is preferably 40 to 150 μm, and more preferably 60 to 130 μm. From the viewpoint of obtaining the above effects, it is preferable that at least one of the cell diameters of the foam particles near the surface and in the center is within the above range, and from the viewpoint of providing a foam molded article with even better effects, it is preferable that both the cell diameters near the surface and in the center of the foam particles are within the above range.

[0080] In this specification, the "cell diameter" of foam particles refers to the average chord length of foam particles that lie in a straight line along the cross-section of the surface of the foam molded body. This average chord length is measured in accordance with ASTM-D-2842-97 using a photograph projecting the cross-section of the foam molded body. This average chord length is calculated by measuring the chord length of each foam particle in a photograph projecting the cross-section of 10 arbitrarily selected foam particles and taking the average value of these measurements. The region from the surface of the foam particle up to 200 μm is defined as the near-surface region, and the region from the center of the foam particle up to 300 μm is defined as the center region. The average value of the chord lengths of 10 foam particles selected from each region is calculated as the cell diameter for each region.

[0081] <2-2. Method for producing recycled polystyrene foam particles> One embodiment of the present invention provides a method for producing recycled polystyrene foam particles, which includes a step of foaming recycled foamable polystyrene resin particles produced by the present manufacturing method. The method for producing recycled polystyrene foam particles according to one embodiment of the present invention (hereinafter sometimes referred to as the method for producing recycled polystyrene foam particles) can be suitably used as a method for producing recycled polystyrene foam particles.

[0082] In the method for producing recycled polystyrene foam particles, the method for foaming the recycled foamable polystyrene resin particles produced by this method is not particularly limited, and known foaming methods can be used. Examples of such known foaming methods include the following method in sequence: (1) placing recycled foamable polystyrene resin particles in a container equipped with a stirrer, (2) heating the recycled foamable polystyrene resin particles with a heat source such as steam, and (3) foaming until a desired foaming ratio is reached to obtain recycled polystyrene foam particles.

[0083] [3. Recycled polystyrene foam molded product] <3-1. Recycled polystyrene foam molded product> In one embodiment of the present invention, a recycled polystyrene foam molded article is provided, which is obtained by molding recycled polystyrene foam particles (i.e., the recycled polystyrene foam particles) produced by the method for producing recycled polystyrene foam particles. The recycled polystyrene foam molded article according to one embodiment of the present invention (hereinafter sometimes referred to as the recycled polystyrene foam molded article) can also be said to be a foam molded article obtained by foaming and molding the recycled foamable resin particles.

[0084] Because this recycled polystyrene foam molded article has the above-mentioned structure, it is a recycled polystyrene foam molded article with excellent strength, even though it uses recycled polystyrene resin particles as a raw material, that is, even though it uses recycled materials as a raw material.

[0085] In this specification, the strength of a foamed molded article is evaluated by the flexural strength measured by the method described in the Examples. Specifically, a foamed molded article with a flexural strength of 0.30 MPa or higher can be said to be a foamed molded article with excellent strength. In other words, this recycled polystyrene-based foamed molded article is a recycled polystyrene-based foamed molded article with a flexural strength of 0.30 MPa or higher.

[0086] The flexural strength of this recycled polystyrene foam molded article is preferably as high as possible, specifically more preferably 0.31 MPa or higher, even more preferably 0.32 MPa or higher, and even more preferably 0.32 MPa or higher. Furthermore, there is no particular upper limit to the flexural strength, but it may be, for example, 0.40 MPa or lower.

[0087] This recycled polystyrene foam molded article exhibits excellent physical properties, including not only flexural strength but also surface elongation, fusion rate, melt strength, and compressive strength. The methods for measuring and evaluating these physical properties are as described in the examples.

[0088] <3-2. Method for producing recycled polystyrene foam molded articles> One embodiment of the present invention provides a method for producing a recycled polystyrene foam molded article, which includes a step of molding recycled polystyrene foam particles (i.e., the recycled polystyrene foam particles) produced by the method for producing recycled polystyrene foam particles. The method for producing a recycled polystyrene foam molded article according to one embodiment of the present invention (hereinafter sometimes referred to as the method for producing the recycled polystyrene foam molded article) can be suitably used as a method for producing the recycled polystyrene foam molded article.

[0089] In the method for manufacturing recycled polystyrene foam molded articles, the method for molding the recycled polystyrene foam particles produced by the method for manufacturing recycled polystyrene foam particles is not particularly limited, and known molding methods can be used. Examples of such known foaming methods include a method in which foam particles are filled into a mold that can be closed but cannot be airtight, and the foam particles are heated and fused together with steam to form a foam molded article; a method in which foam particles are filled into a closed mold having a desired shape and having many small holes drilled in its walls, a heating medium such as steam is ejected from the mold holes to heat the foam particles to a temperature above their softening point, causing them to fuse together, and then removed from the mold after a cooling process. [Examples]

[0090] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is... The examples are not limited to those described below. In the examples, comparative examples, and tables below, "part" refers to... Unless otherwise specified, "%" refers to weight-based figures (parts by weight and weight %).

[0091] [Measurement and evaluation methods] The physical properties in the examples and comparative examples were measured and evaluated using the following methods.

[0092] <Weight-average molecular weight of recycled polystyrene resin particles and recycled foamed polystyrene resin particles> A sample was prepared by weighing 0.02 g of recycled polystyrene resin particles or recycled foamed polystyrene resin particles and dissolving them in 20 ml of tetrahydrofuran. This sample was subjected to gel permeation chromatography (measuring instrument: HLC-8020, manufactured by Tosoh Corporation; column: TSKgel Super HZM-H; column temperature: 40°C; flow rate: 0.35 ml / min). The weight-average molecular weight (g / mol) of the sample was calculated by comparing the obtained data with a calibration curve for standard polystyrene.

[0093] <Remaining styrene content of recycled polystyrene resin particles and recycled foamed polystyrene resin particles> 0.25 g of recycled polystyrene resin particles or recycled foamed polystyrene resin particles were weighed out and dissolved in 20 ml of methylene chloride along with internal standard cyclopentanol to prepare the measurement sample. The amount of residual styrene in each resin particle was measured using a gas chromatograph (GC-2014) manufactured by Shimadzu Corporation. The gas chromatography conditions were as follows: Capillary column: GL Sciences Rtx-1 Column temperature conditions: Heat from 50°C to 80°C at a rate of 3°C / min, then heat from 80°C to 180°C at a rate of 10°C / min. Carrier gas: Helium.

[0094] Using a calibration curve created from pure styrene monomer, the styrene content in each resin particle was calculated from the obtained results.

[0095] Furthermore, the amount of residual styrene in recycled foamed polystyrene resin particles was evaluated according to the following criteria. A (Excellent): 1000 ppm or less B (Pass): More than 1000ppm, less than 3000ppm C (defective): Over 3000ppm.

[0096] <Moisture content of recycled foamed polystyrene resin particles> 0.04 g of recycled foamed polystyrene resin particles, the target of measurement, were placed in a measuring bottle, and their moisture content was measured using an AQ-2200A (moisture meter). The measurement conditions were as follows: Evaporation chamber temperature: 150℃ Carrier gas: Nitrogen (0.1 MPa) Carrier gas flow rate: 150cc / min Karl Fischer Solution: Aqualight RS-A.

[0097] <Surface elongation of recycled polystyrene foam molded articles> The surface of the fabricated recycled polystyrene foam molded body was visually inspected, and the surface elongation was confirmed according to the following criteria. A (Excellent): No gaps between grains, extremely beautiful. B (Pass): There are only a few small gaps between the grains, beautiful. C (Slightly Poor): There are gaps between the grains, and the appearance is slightly poor. D (Defective): Numerous gaps between grains, resulting in a poor appearance.

[0098] <Fusion rate of recycled polystyrene foam molded material> The fusion rate was confirmed using the following method with the fabricated recycled polystyrene foam molded body: The central part of the recycled polystyrene foam molded body in the longitudinal direction was bent along the width direction to break the foam molded body. The resulting fracture surface was visually observed, and the number of all recycled polystyrene foam particles constituting the fracture surface and the number of recycled polystyrene foam particles that fractured outside the particle interface were measured, and the fusion rate was calculated based on the following formula. Fusion rate (%) = (Number of recycled polystyrene foam particles fractured at locations other than the particle interface on the fracture surface / Total number of recycled polystyrene foam particles constituting the fracture surface) × 100. A (Particularly excellent): Fusion rate of 90% or higher B (Excellent): Fusion rate of 70% or more, but less than 90% C (Pass): Fusion rate is 50% or more, but less than 70%. D (Defective): Fusion rate is less than 50%.

[0099] <Melt of recycled polystyrene foam molded material> The surface of the fabricated recycled polystyrene foam molded body was visually inspected, and melting was confirmed according to the following criteria. A (Excellent): The surface of the recycled polystyrene foam molded product is completely free of molten areas. B (Pass): Only a portion of the surface of the recycled polystyrene foam molded product is melted. C (Defective): The surface of the recycled polystyrene foam molded article has molten areas throughout.

[0100] <Compression test of recycled polystyrene foam molded material> The fabricated recycled polystyrene foam molded material was cut to create five test samples measuring 50 × 50 × 25(t) mm. The compressive strength of these test samples was measured using a strength testing machine (SHIMADZU AGX-V, load cell SLBL-5kN) at a compression speed of 10 mm / min.

[0101] <Bending test of recycled polystyrene foam molded material> Five test specimens measuring 350 × 100 × 25(t) mm were prepared by cutting a recycled polystyrene foam molded body. The bending strength and fracture point displacement of these test specimens were measured using a strength testing machine (SHIMADZU AGX-V, load cell SLBL-5kN) at a bending speed of 20 mm / min.

[0102] [Example 1] <Manufacturing of recycled foamed polystyrene resin particles> Recycled polystyrene resin particles with a weight-average molecular weight of 189,000 (g / mol) (major diameter: 1.07 mm, minor diameter: 0.77 mm, particle weight: 0.75 mg / particle) were used as the seed resin.

[0103] (Polymerization process) In a 6L autoclave equipped with a stirrer, 93.5 parts by weight of pure water, 0.038 parts by weight of tricalcium phosphate, 0.0104 parts by weight of sodium α-olefin sulfonate, 0.1 part by weight of sodium chloride, and 50 parts by weight of seed resin were charged, and stirring was started. Subsequently, the temperature was raised to 92°C. Upon reaching 92°C, styrene monomer, polymerization initiator, and other additives were added stepwise according to the following formulation, and polymerization was started.

[0104] (1) From the start of polymerization (0 hours) to 1 hour later: Styrene monomer was added at a rate of 0.24 parts / min (total 14.6 parts), and a polymerization initiator (benzoyl peroxide, 10-hour half-life temperature of 73.6°C) with a 10-hour half-life temperature of 50°C or higher and less than 90°C was added at a rate of 0.0175 parts every 15 minutes (total 0.070 parts).

[0105] (2) From 1 hour to 2 hours after the start of polymerization: Styrene monomer was added at a rate of 0.295 parts / min (total 17.7 parts), and a polymerization initiator (benzoyl peroxide) with a 10-hour half-life temperature of 50°C or higher and less than 90°C was added at a rate of 0.01175 parts every 15 minutes (total 0.047 parts).

[0106] (3) Two hours after the start of polymerization, 0.18 parts of a dispersant (tricalcium phosphate) was added.

[0107] (4) 2 hours to 3 hours after the start of polymerization: Styrene monomer was added at a rate of 0.295 parts / min (total 17.7 parts), and a polymerization initiator (benzoyl peroxide) with a 10-hour half-life temperature of 50°C or higher and less than 90°C was added at a rate of 0.00575 parts every 15 minutes (total 0.023 parts).

[0108] (5) 2 hours and 30 minutes after the start of polymerization, 0.064 parts of a polymerization initiator (1,1-di(t-butylperoxy)cyclohexane, with a 10-hour half-life temperature of 90.7°C or higher) was added.

[0109] At 3.0 hours after the start of polymerization, the addition of styrene monomer, polymerization initiator, and other additives was completed, and the polymerization process was terminated. The time required for the polymerization process was 3.0 hours. Subsequently, the system was maintained at 92°C for a further 30 minutes (holding step).

[0110] (Impregnation process) After the above process, 1.0 part by weight of cyclohexane and 6.8 parts by weight of n-rich butane (n-butane / isobutane = 70 / 30%) were added to the system containing polystyrene resin particles, and the temperature was raised to 121°C. After maintaining the system at 121°C for 1 hour and 45 minutes, it was cooled to room temperature, and the polymerization slurry was removed from the autoclave. The removed polymerization slurry was washed, dehydrated, and dried to obtain recycled expandable polystyrene resin particles. The physical properties of the obtained recycled expandable polystyrene resin particles were measured and evaluated. The results are shown in Table 1. For each evaluation, particles that passed through a 2.0 mm sieve but remained on (did not pass through) a 0.5 mm sieve were used. The major diameter of the recycled expandable polystyrene resin particles was 1.80 mm, the minor diameter was 1.55 mm, and the particle weight was 1.55 mg / particle.

[0111] (Addition of external additives) 100 parts by weight (765 g) of the obtained recycled foamed polystyrene resin particles, along with 0.15 parts by weight of zinc stearate and 0.07 parts by weight of castor wax as external additives, were placed in a polyethylene bag. The bag was then vigorously shaken 100 times with the opening closed to add the external additives to the recycled foamed polystyrene resin particles. The mixture was then stored in a stainless steel container for two weeks.

[0112] <Manufacturing of recycled polystyrene foam particles> 100 parts by weight (765 g) of recycled foamable polystyrene resin particles obtained in the above process were loaded into a pressurized pre-foaming machine (Daikai Kogyo Co., Ltd., BHP-110). Foaming (pre-foaming) was performed while adjusting the internal pressure of the machine from 0.005 to 0.015 MPa with a blowing vapor pressure of 0.1 MPa, obtaining recycled polystyrene foam particles with a bulk ratio of 50. The cell diameter (average chord length) of the obtained recycled polystyrene foam particles was 130 μm both near the surface and in the center.

[0113] <Manufacturing of recycled polystyrene foam molded products> The recycled polystyrene foam particles obtained in the above process were filled into a mold installed in a molding machine (DAISEN Corporation, KR-57LB-MC), and heated for 16 seconds at a blowing vapor pressure of 0.7 MPa and a molding pressure of 70 kPa / 80 kPa (fixed side / moving side) or 80 kPa / 90 kPa (fixed side / moving side), followed by 5 seconds of water cooling to obtain a recycled polystyrene foam molded body measuring 450 × 300 × 25 mm. The physical properties of the obtained recycled polystyrene foam molded body were measured and evaluated. The results are shown in Table 2.

[0114] [Example 2] Except for using recycled polystyrene resin particles (major diameter: 1.14 mm, minor diameter: 0.85 mm, particle weight: 0.77 mg / particle) with a weight-average molecular weight of 246,000 (g / mol) as the seed resin, recycled foamable polystyrene resin particles, recycled polystyrene foam particles, and recycled polystyrene foam molded articles were obtained by the same procedure as in Example 1, and their physical properties were measured and evaluated. The results are shown in Tables 1 and 2. The obtained recycled foamable polystyrene resin particles had a major diameter of 1.85 mm, a minor diameter of 1.62 mm, and a particle weight of 1.60 mg / particle. In addition, the cell diameter (average chord length) of the obtained recycled polystyrene foam particles was 135 μm both near the surface and in the center.

[0115] [Examples 3 and 4] Except for using t-butyl peroxy-2-ethylhexyl monocarbonate (10-hour half-life temperature: 99°C) as a polymerization initiator with a 10-hour half-life temperature of 90°C or higher, in the amount shown in Table 1, recycled foamable polystyrene resin particles, recycled foam particles, and recycled foam molded articles were obtained by the same procedure as in Example 1, and their physical properties were measured and evaluated. The results are shown in Tables 1 and 2. The recycled foamable polystyrene resin particles obtained in Examples 3 and 4 had a major diameter of 1.80 mm, a minor diameter of 1.55 mm, and a particle weight of 1.55 mg / particle. In addition, the cell diameter (average chord length) of the obtained recycled foam particles was 130 μm both near the surface and in the center.

[0116] [Example 5] Except for using recycled polystyrene resin particles (major diameter: 1.11 mm, minor diameter: 0.81 mm, particle weight: 0.76 mg) with a weight-average molecular weight of 263,000 (g / mol) as the seed resin, recycled foamable polystyrene resin particles, recycled polystyrene foam particles, and recycled polystyrene foam molded articles were obtained by the same procedure as in Example 1, and their physical properties were measured and evaluated. The results are shown in Tables 1 and 2. The obtained recycled foamable polystyrene resin particles had a major diameter of 1.80 mm, a minor diameter of 1.58 mm, and a particle weight of 1.57 mg / particle. In addition, the cell diameter (average chord length) of the obtained recycled polystyrene foam particles was 125 μm both near the surface and in the center.

[0117] [Example 6] Except for adding divinylbenzene (DVB), a crosslinking agent, 2 hours and 45 minutes after the start of polymerization, the same procedure as in Example 1 was used to obtain recycled foamable polystyrene resin particles, recycled polystyrene foam particles, and recycled polystyrene foam molded articles. The physical properties of each were measured and evaluated. The results are shown in Tables 1 and 2. The obtained recycled foamable polystyrene resin particles had a major diameter of 1.80 mm, a minor diameter of 1.55 mm, and a particle weight of 1.55 mg / particle. The cell diameter (average chord length) of the obtained foam particles was 130 μm both near the surface and in the center.

[0118] [Example 7] Except for the following changes to the formulation of each component in the polymerization process, recycled foamed polystyrene resin particles, recycled polystyrene foam particles, and recycled polystyrene foam molded articles were obtained by the same procedure as in Example 1, and their physical properties were measured and evaluated. The results are shown in Tables 1 and 2. The recycled foamed polystyrene resin particles had a major diameter of 1.80 mm, a minor diameter of 1.55 mm, and a particle weight of 1.55 mg / particle. The cell diameter (average chord length) of the obtained foam particles was 130 μm both near the surface and in the center.

[0119] (polymerization formula) (1) 2 hours to 3 hours after the start of polymerization: Styrene monomer was added at a rate of 0.295 parts / min (total 17.7 parts), and a polymerization initiator (benzoyl peroxide) with a 10-hour half-life temperature of 50°C or higher and less than 90°C was added at a rate of 0.00575 parts every 15 minutes (total 0.023 parts).

[0120] (2) From 1 hour to 2 hours after the start of polymerization: Styrene monomer was added at a rate of 0.295 parts / min (total 17.7 parts), and a polymerization initiator (benzoyl peroxide) with a 10-hour half-life temperature of 50°C or higher and less than 90°C was added at a rate of 0.01175 parts every 15 minutes (total 0.047 parts).

[0121] (3) Two hours after the start of polymerization, 0.18 parts of a dispersant (tricalcium phosphate) was added.

[0122] (4) From the start of polymerization (0 hours) to 1 hour later: Styrene monomer was added at a rate of 0.24 parts / min (total 14.6 parts), and a polymerization initiator (benzoyl peroxide) with a 10-hour half-life temperature of 50°C or higher and less than 90°C was added at a rate of 0.0175 parts every 15 minutes (total 0.070 parts).

[0123] (5) 2 hours and 30 minutes after the start of polymerization, 0.064 parts of a polymerization initiator (1,1-di(t-butylperoxy)cyclohexane, with a 10-hour half-life temperature of 90.7°C or higher) was added.

[0124] [Table 1]

[0125] [Table 2]

[0126] [Comparative Example 1] <Manufacturing of recycled foamed polystyrene resin particles> Recycled polystyrene resin particles with a weight-average molecular weight of 246,000 (g / mol) (major diameter: 1.14 mm, minor diameter: 0.85 mm, particle weight: 0.77 mg / particle) were used as the seed resin.

[0127] (Polymerization process) In a 6L autoclave equipped with a stirrer, 200 parts by weight of pure water, 0.50 parts by weight of tricalcium phosphate, 0.0105 parts by weight of sodium α-olefin sulfonate, 1.25 parts by weight of sodium chloride, and 100 parts by weight of seed resin were charged, and stirring was started. Subsequently, the temperature was raised to 100°C. Upon reaching 100°C, 6 parts by weight of pentane were added to the system. After adding pentane, the system was heated to 118°C and maintained at that temperature for 5 hours. After cooling to room temperature, the polymerization slurry was removed from the autoclave, and the removed polymerization slurry was washed, dehydrated, and dried to obtain recycled expandable polystyrene resin particles. The physical properties of the obtained recycled expandable polystyrene resin particles were measured and evaluated. The results are shown in Tables 3 and 4. The obtained recycled expandable polystyrene resin particles had a major diameter of 1.1 mm, a minor diameter of 1.05 mm, and a particle weight of 0.77 mg / particle.

[0128] <Foaming and Molding> Using the recycled foamable polystyrene resin particles obtained by the above procedure, recycled polystyrene foam particles and recycled polystyrene foam molded articles were obtained by the same procedure as in Example 1, and their physical properties were measured and evaluated. The results are shown in Tables 3 and 4. The cell diameter (average chord length) of the obtained recycled polystyrene foam particles was 10 μm near the surface and 150 μm in the center.

[0129] [Comparative Example 2] Recycled polystyrene resin particles (major diameter: 1.00 mm, minor diameter: 0.9 mm) with a weight-average molecular weight of 175,000 (g / mol) were used as the seed resin, and recycled foamable polystyrene resin particles were obtained using the same procedure as in Japanese Patent Application Publication No. 2002-348400. The measurement and evaluation results of each physical property of the obtained recycled foamable polystyrene resin particles are shown in Table 3.

[0130] Using the recycled foamable polystyrene resin particles obtained by the above procedure, recycled polystyrene foam particles and recycled polystyrene foam molded articles were obtained by the same procedure as in Example 1, and their physical properties were measured and evaluated. The results are shown in Table 4. The obtained recycled foamable polystyrene resin particles had a major diameter of 1.51 mm, a minor diameter of 1.35 mm, and a particle weight of 1.2 mg / particle. The cell diameter (average chord length) of the obtained recycled polystyrene foam particles was 10 μm near the surface and 160 μm in the center.

[0131] [Comparative Example 3] Except for using the type and amount of polymerization initiator as shown in Table 3, recycled foamable polystyrene resin particles, recycled foamed polystyrene particles, and recycled foamed molded articles were obtained using the same procedure as in Example 1, and their physical properties were measured and evaluated. The results are shown in Tables 3 and 4. The obtained recycled foamable polystyrene resin particles had a major diameter of 1.80 mm, a minor diameter of 1.55 mm, and a particle weight of 1.55 mg / particle. The cell diameter (average chord length) of the obtained recycled foamed polystyrene particles was 130 μm both near the surface and in the center.

[0132] [Table 3]

[0133] [Table 4] [Industrial applicability]

[0134] According to one embodiment of the present invention, recycled foamable polystyrene resin particles can be provided that can provide a recycled polystyrene foam molded article with excellent strength while using recycled materials as raw materials. Therefore, one embodiment of the present invention can be suitably used in fields such as packaging materials (trays) for food containers, transport packaging materials such as fish boxes, and insulation materials (for example, hot water storage tanks, roof insulation materials, pipe insulation materials, temperature-controlled storage containers, temperature-controlled transport containers, etc.).

Claims

1. A polymerization step in which recycled polystyrene resin particles are used as a seed resin and styrene monomers are polymerized onto the seed resin, The process includes an impregnation step in which a highly volatile foaming agent is impregnated into the polystyrene resin particles obtained in the polymerization step, In the polymerization step, of the total amount of the seed resin and the styrene monomer used (100 parts by weight), the amount of the seed resin used is 50 parts by weight or more, and the amount of the styrene monomer used is 50 parts by weight or less. The polymerization step includes a step of increasing the weight-average molecular weight of the seed resin to 30,000 (g / mol) or more. A method for producing recycled foamed polystyrene resin particles having a weight-average molecular weight of 250,000 (g / mol) or more.

2. The method for producing recycled foamed polystyrene resin particles according to claim 1, wherein the weight-average molecular weight of the recycled foamed polystyrene resin particles is 335,000 or less (g / mol).

3. In the polymerization step, The amount of polymerization initiator added at the point when one-third of the total polymerization time has elapsed is 25% to 50% of the total amount of polymerization initiator added. A method for producing recycled foamable polystyrene resin particles according to claim 1, wherein the amount of polymerization initiator added when two-thirds of the total polymerization time has elapsed is 50% to 95% of the total amount of polymerization initiator added.

4. The method for producing recycled foamable polystyrene resin particles according to claim 1, wherein the seed resin contains 50 parts by weight or more of recycled polystyrene resin particles having a major axis of 0.9 to 1.2 mm and a minor axis of 0.6 to 0.9 mm in 100 parts by weight of the total amount of the seed resin.

5. The method for producing recycled foamable polystyrene resin particles according to claim 1, wherein the total amount of polymerization initiator added in the polymerization step is 0.12 to 0.50 parts by weight with respect to 100 parts by weight of the total amount of seed resin and styrene monomer used.

6. A method for producing recycled foamable polystyrene resin particles according to claim 1, wherein the polymerization time in the polymerization step is 3.5 hours or less.

7. The method for producing recycled foamable polystyrene resin particles according to claim 1, wherein in the polymerization step, a polymerization initiator having a half-life temperature of 90°C or higher for 10 hours is added in an amount of 0.01 to 0.30 parts by weight per 100 parts by weight of the total amount of the seed resin and the styrene monomer used.

8. The method for producing regenerative foamable polystyrene resin particles according to claim 7, wherein the polymerization initiator having a 10-hour half-life temperature of 90°C or higher is a polymerization initiator having a carbonate structure.

9. A method for producing recycled foamed polystyrene resin particles according to claim 1, wherein the water content of the recycled foamed polystyrene resin particles is greater than 0.5%.

10. A method for producing recycled foamable polystyrene resin particles according to claim 1, wherein the residual styrene content of the recycled polystyrene resin particles is 200 ppm or more.

11. A method for producing recycled polystyrene foamed particles, comprising the step of foaming recycled foamable polystyrene resin particles produced by the manufacturing method described in any one of claims 1 to 10.

12. A method for producing a recycled polystyrene foam molded article, comprising the step of molding recycled polystyrene foam particles produced by the manufacturing method described in claim 11.

13. Recycled foamed polystyrene resin particles having a weight-average molecular weight of 250,000 (g / mol) or more and a water content of more than 0.5%.

14. Recycled foamable polystyrene resin particles according to claim 13, wherein the weight-average molecular weight is 335,000 (g / mol) or less.

15. Recycled foamable polystyrene resin particles according to claim 13, wherein the residual styrene content is 5000 ppm or less.

16. A recycled polystyrene foam molded article, which is made by molding recycled polystyrene foam particles obtained by foaming recycled foamable polystyrene resin particles according to any one of claims 13 to 15, and which has a bending strength of 0.30 MPa or more.

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