Chemical blowing agent composition, chemical blowing agent masterbatch, foam, and method for producing foam

Abstract

The present invention addresses the problem of providing a chemical foaming agent composition and a chemical foaming agent master batch, each of which is capable of achieving a good balance between miniaturization of air bubbles and suppression of decrease in flame retardancy if used for molding of a foam. The present invention provides: a foam which is produced using the above-described chemical foaming agent composition or chemical foaming agent master batch, and which has achieved both miniaturization of air bubbles and suppression of decrease in flame retardancy; and a method for producing this foam. A thermoplastic resin composition according to the present invention is a chemical foaming agent composition which contains sodium hydrogen carbonate and an acidic substance, wherein the acidic substance is an inorganic compound or an organic compound that has a melting point of 400°C or more.

Description

Technical Field

[0001] The present invention relates to a chemical blowing agent composition, a chemical blowing agent masterbatch, a foam, and a method for producing a foam. More specifically, the present invention relates to a chemical blowing agent composition and a chemical blowing agent masterbatch capable of achieving both fine bubble formation and suppression of flame retardancy reduction when used for molding a foam, and further to a foam in which both fine bubble formation and suppression of flame retardancy reduction are achieved using the chemical blowing agent composition or the chemical blowing agent masterbatch, and a method for producing the same.

Background Art

[0002] Injection foam molding is increasingly being adopted for molding foams of resins or elastomers used for exterior parts and structural parts used in automobiles, electric appliances, etc. in order to suppress sink marks (such as dents caused by molding shrinkage) and warpage. Among them, for parts produced in small lots, if a chemical foaming method with low equipment investment is selected, the unit price of the product will be low, which is advantageous in terms of cost.

[0003] In the chemical foaming method, a chemical blowing agent that generates gas by thermal decomposition or chemical reaction is used. In the past, the foams obtained by the chemical foaming method had problems such as deterioration of appearance quality and reduction of strength due to large internal bubble diameters. However, in recent years, a technique for refining bubbles by adding a foaming aid together with a chemical blowing agent to a resin or an elastomer has been developed, and quality that is not a problem even for exterior parts and structural parts can be ensured.

[0004] The “chemical blowing agent” refers to a compound that generates gas (bubbles) by thermal decomposition or chemical reaction among the chemicals mixed with a resin or the like to obtain a foam. The “chemical blowing agent composition” refers to a composition composed of a chemical blowing agent and an auxiliary agent which is a component other than the chemical blowing agent. The “chemical blowing agent masterbatch” is a composition in which a chemical blowing agent or a chemical blowing agent composition is mixed with a thermoplastic resin or a thermoplastic elastomer.

[0005] For example, Patent Document 1 describes a method for producing a foaming agent composition and a thermoplastic resin foam, which are foamed and molded with fine bubbles by adding a foaming agent composition containing a pyrolysis-type foaming agent, citrate, and a lithium compound (excluding lithium salts) or zinc oxide to a thermoplastic resin.

[0006] Furthermore, Patent Document 2 describes a foaming agent composition used for molding resin foams, which contains a predetermined amount each of sodium bicarbonate, lithium stearate, monosodium citrate, and at least one of zinc, talc, and silica, all of which are thermal decomposition type foaming agents. Patent Document 2 also describes that by using this foaming agent composition to foam-molde a resin, it is possible to obtain a foam with fine and uniformly distributed bubbles, resulting in a foam with excellent appearance, such as planar smoothness, and substrate performance.

[0007] Here, the parts for automobiles, electrical appliances, etc., require not only foam properties but also flame retardancy. Therefore, when molding the foam, flame retardants are added as appropriate depending on the type of resin. However, a problem has been that foams obtained using foaming agent compositions that combine the pyrolysis-type foaming agents described in Patent Documents 1 and 2 with the above-mentioned predetermined components have reduced flame retardancy regardless of the type of resin and flame retardant. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 4196238 [Patent Document 2] Patent No. 4110032 [Overview of the project] [Problems that the invention aims to solve]

[0009] This invention has been made in view of the above-mentioned problems and circumstances, and its objective is to provide a chemical blowing agent composition and a chemical blowing agent masterbatch that can achieve both miniaturization of bubbles and suppression of flame retardancy reduction when used in the molding of a foam. Furthermore, it is also objective to provide a foam produced using the above-mentioned chemical blowing agent composition or chemical blowing agent masterbatch that achieves both miniaturization of bubbles and suppression of flame retardancy reduction, and a method for producing the same. [Means for solving the problem]

[0010] In order to solve the above problems, the inventors, in the process of investigating the causes of the above problems, selected sodium bicarbonate as a chemical blowing agent and selected a specific acidic substance as a blowing aid to combine with it to form a chemical blowing agent composition. They found that the foam obtained using this chemical blowing agent composition achieves both miniaturization of bubbles and suppression of the decrease in flame retardancy, leading to the present invention. In other words, the above problems according to the present invention are solved by the following means.

[0011] 1. A chemical blowing agent composition containing sodium bicarbonate and an acidic substance, The acidic substance is at least one selected from sodium dihydrogen phosphate and sodium bisulfite. Furthermore, when the total of the sodium bicarbonate and the acidic substance is considered to be 100% by mass, the sodium bicarbonate is in the range of 10 to 20% by mass, and the acidic substance is in the range of 90 to 80% by mass. A chemical blowing agent composition.

[0012] 2. The chemical blowing agent composition according to item 1, wherein the total amount of the chemical blowing agent composition contains an organic compound having a melting point of less than 400°C in an amount of 58% by mass or less.

[0014] 3 .Section 1 or The In item 2 A chemical blowing agent masterbatch containing the chemical blowing agent composition described above and a thermoplastic resin or thermoplastic elastomer.

[0015] 4 .Section 1 or The In item 2 The chemical blowing agent composition described or 3A foam obtained by foam-molding a foam material containing the chemical foaming agent masterbatch according to the item and a thermoplastic resin or a thermoplastic elastomer.

[0016] 5 . The content ratio of the organic compound having a melting point of less than 400 ° C derived from the chemical foaming agent composition with respect to the total amount of the foam is within the range of 1% by mass or less. The foam according to item 4 described above.

[0017] 6 . The thermoplastic resin or thermoplastic elastomer includes at least one selected from the group consisting of a polyolefin resin, an acrylonitrile-butadiene-styrene resin, a polystyrene resin, a polyamide resin, a polyvinyl chloride resin, an ethylene vinyl acetate resin, and a thermoplastic elastomer. The foam according to item 4 described above or item 5 described above.

[0018] 7 . Further, a foam according to any one of items 4 to 6 described above, which contains a flame retardant.

[0019] 8 . Item 1 or The chemical foaming agent composition described in item In item 2 described above or the chemical foaming agent masterbatch described in item 3 described above, and a thermoplastic resin or a thermoplastic elastomer are mixed to obtain a foam material, and the foam material is foam-molded by an injection molding machine. A method for producing a foam having

[0020] 9 . The ratio of the chemical foaming agent composition with respect to the total amount of the thermoplastic resin or thermoplastic elastomer in the foam material is within the range of 0.1 to 1.7% by mass. The method for producing a foam according to item 8 described above.

Advantages of the Invention

[0021] The present invention provides a chemical blowing agent composition and a chemical blowing agent masterbatch that can achieve both miniaturization of bubbles and suppression of flame retardancy reduction when used in the molding of a foam. Furthermore, it provides a foam produced using the above chemical blowing agent composition or chemical blowing agent masterbatch that achieves both miniaturization of bubbles and suppression of flame retardancy reduction, as well as a method for producing the same.

[0022] Although the mechanism by which the effects of this invention manifest or the mechanism of action are not yet clear, we speculate as follows.

[0023] Sodium bicarbonate decomposes upon heating or acid, generating CO2 as shown in the following equations (1) or (2). Formula (1): 2NaHCO3→Na2CO3+H2O+CO2 Formula (2): NaHCO3+HA→NaA+H2O+CO2 (In equation (2), HA is a proton H + This represents an acid that releases a compound. (A represents the conjugate base of acid HA.)

[0024] When sodium bicarbonate is mixed with resin or elastomer, molded, and heated, the CO2 generated by the decomposition reaction of sodium bicarbonate due to heat or acid forms bubbles within the matrix of the resin or elastomer, resulting in a foamed material.

[0025] Conventionally, it has been known that combining sodium bicarbonate with organic acid compounds such as citrate as a foaming agent can refine the bubbles in the foam. It is also believed that using inorganic substances such as talc, silica, and calcium carbonate as foaming agents can refine the bubbles in the foam. Normally, when sodium bicarbonate decomposes and foams within a resin, the size of the bubbles in the foam is thought to increase due to the bonding of bubbles or the rupture of bubbles, allowing them to connect with each other. The presence of a foaming agent in the system is thought to allow the foaming agent to act as a bubble nucleus, increasing the number of bubbles, and consequently suppressing bubble bonding and rupture, thereby contributing to the refinement of the foam.

[0026] The inventors investigated inorganic compounds from the viewpoint of suppressing the decrease in flame retardancy of the resulting foam, and found that among inorganic compounds, acidic substances in particular are excellent in their ability to refine bubbles with sodium bicarbonate while suppressing the decrease in flame retardancy of the foam. Furthermore, they found that even organic compounds can produce the same effect as inorganic acidic substances if they are acidic substances with a melting point of 400°C or higher.

[0027] When sodium bicarbonate is used alone, it generates bubbles (CO2 gas) by thermal decomposition as shown in formula (1). In the chemical blowing agent composition of the present invention, sodium bicarbonate undergoes a chemical reaction with the above-mentioned acidic substance as shown in formula (2), generating bubbles (CO2 gas). Here, the decomposition temperature of sodium bicarbonate is given as 270°C, but the decomposition reaction in formula (1) is known to occur gradually from approximately 50°C. However, the chemical reaction in formula (2) is thought to occur at a lower temperature than the reaction in formula (1).

[0028] Thus, sodium bicarbonate reacts with acidic substances as shown in equation (2) to generate bubbles (CO2 gas) at low temperatures. Furthermore, when foaming occurs at such low temperatures, the matrix, such as resin or elastomer, is in a highly viscous state, making it difficult for the bubbles formed from the foamed gas to coalesce. As a result, we believe this contributes to the miniaturization of the foam.

[0029] Furthermore, in the thermal decomposition of elemental sodium bicarbonate according to equation (1), one molecule of CO2 is produced from two molecules of sodium bicarbonate, whereas in the reaction of sodium bicarbonate with an acidic substance according to equation (2), one molecule of CO2 is produced for every one molecule of sodium bicarbonate. In other words, we believe that the increase in the amount of gas produced contributes to the finer development of foam.

[0030] Furthermore, regarding the ability to suppress the decrease in flame retardancy, it was hypothesized that among acidic substances, organic compounds become more flammable because they generate flammable gases during combustion. However, the inventors found that if an organic compound (acidic substance) with a high melting point (400°C or higher) is used as the acidic substance, the flame retardancy hardly decreases. The reason why the flame retardancy does not decrease with organic compounds with a high melting point (400°C or higher) is hypothesized that such organic compounds generate flammable gases at a delayed rate, and flammable gases are not generated before the fire is extinguished. [Brief explanation of the drawing]

[0031] [Figure 1] A graph showing the relationship between the pH of the compound used in combination with sodium bicarbonate and the bubble diameter of the resulting foam. [Modes for carrying out the invention]

[0032] The chemical blowing agent composition of the present invention is a chemical blowing agent composition containing sodium bicarbonate and an acidic substance, characterized in that the acidic substance is an inorganic compound or an organic compound with a melting point of 400°C or higher. This characteristic is a technical feature common to each embodiment of the following chemical blowing agent compositions.

[0033] In embodiments of the chemical blowing agent composition of the present invention, the chemical blowing agent composition may contain an organic compound having a melting point of less than 400°C. In this case, from the viewpoint of suppressing a decrease in flame retardancy, it is preferable that the content ratio of the organic compound having a melting point of less than 400°C relative to the total amount of the chemical blowing agent composition be within the range of 58% by mass or less.

[0034] As an embodiment of the chemical blowing agent composition of the present invention, from the viewpoint of exhibiting the effects of the present invention, it is preferable that the acidic substance includes at least one selected from boric acid, diboron trioxide, sodium dihydrogen phosphate, and sodium bisulfite.

[0035] The chemical blowing agent masterbatch of the present invention contains the chemical blowing agent composition of the present invention and a thermoplastic resin or thermoplastic elastomer.

[0036] The foam of the present invention is characterized by being foamed and molded from a foaming material containing the chemical blowing agent composition or chemical blowing agent masterbatch of the present invention and a thermoplastic resin or thermoplastic elastomer.

[0037] In embodiments of the foam of the present invention, from the viewpoint of flame retardancy, it is preferable that the content ratio of the organic compound derived from the chemical blowing agent composition, which has a melting point of less than 400°C, relative to the total amount of the foam, is within the range of 1% by mass or less.

[0038] As an embodiment of the foam of the present invention, from the viewpoint of achieving the effects of the present invention, it is preferable that the thermoplastic resin or thermoplastic elastomer comprises at least one selected from polyolefin resin, acrylonitrile-butadiene-styrene resin, polystyrene resin, polyamide resin, polyvinyl chloride resin, ethylene vinyl acetate resin, and thermoplastic elastomer.

[0039] As an embodiment of the foam of the present invention, from the viewpoint of achieving the effects of the present invention, the foam may further contain a flame retardant.

[0040] The present invention provides a method for producing a foam, comprising the steps of: mixing the chemical foaming agent composition or chemical foaming agent masterbatch of the present invention with a thermoplastic resin or thermoplastic elastomer to obtain a foaming material; and foaming the foaming material using an injection molding machine.

[0041] As an embodiment of the method for producing the foam of the present invention, from the viewpoint of flame retardancy, it is preferable that the ratio of the chemical blowing agent composition to the total amount of the thermoplastic resin or thermoplastic elastomer in the foam material is within the range of 0.1 to 1.7% by mass.

[0042] The present invention, its components, and embodiments for carrying out the present invention will be described in detail below. In this application, "~" is used to mean that the numerical values ​​before and after it are included as the lower and upper limits. In this specification, "main component," "mainly contained," and "consisting of as the main component" mean that the main component accounts for 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more of the whole.

[0043] [Chemical blowing agent composition] The chemical blowing agent composition of the present invention is a chemical blowing agent composition containing sodium bicarbonate and an acidic substance, characterized in that the acidic substance is an inorganic compound or an organic compound with a melting point of 400°C or higher. As described above, the chemical blowing agent composition is a composition consisting of a chemical blowing agent and auxiliary agents which are components other than the chemical blowing agent. Examples of auxiliary agents include blowing aids, drip inhibitors, antioxidants, lubricants, dispersants, nucleating agents, etc. The chemical blowing agent composition of the present invention contains sodium bicarbonate as the chemical blowing agent and contains the above-mentioned acidic substance as an auxiliary agent (blowing aid).

[0044] In the chemical blowing agent composition of the present invention, sodium bicarbonate is used as a chemical blowing agent. Sodium bicarbonate decomposes as shown in formula (1) or formula (2) above to generate CO2 gas, which forms bubbles in the matrix of, for example, a thermoplastic resin or thermoplastic elastomer (hereinafter sometimes referred to as "resin, etc."). The chemical blowing agent composition of the present invention is used to form a foam. The foam consists of a matrix mainly composed of resin, etc. and bubbles.

[0045] The acidic substance (hereinafter referred to as "acidic substance A") contained in the chemical blowing agent composition of the present invention is an inorganic compound or an organic compound with a melting point of 400°C or higher. The acidic substance according to the present invention contains protons H in the presence of water or an aqueous medium. +The present invention also includes substances that produce an acid capable of dissociating (e.g., diboron trioxide). In the chemical blowing agent composition of the present invention, acidic substance A functions as a blowing aid that helps the chemical blowing agent sodium bicarbonate to blow.

[0046] Hereinafter, acidic substances that are inorganic compounds will also be referred to as "acidic substance A1," and acidic substances that are organic compounds with a melting point of 400°C or higher will also be referred to as "acidic substance A2." Acidic substance A functions to cause CO2 gas generated from sodium bicarbonate to exist as fine-diameter bubbles within the matrix of resin, etc. In addition, acidic substance A does not cause a decrease in the flame retardancy of the resin, etc. that constitute the matrix of the foam, and preferably has the property of improving flame retardancy. The evaluation method for bubble diameter and flame retardancy in the foam will be described later.

[0047] The chemical blowing agent composition of the present invention may contain optional components other than sodium bicarbonate and acidic substance A, as long as they do not impair the effects of the present invention. Examples of optional components include chemical blowing agents other than sodium bicarbonate, blowing aids other than acidic substance A, drip inhibitors, antioxidants, lubricants, dispersants, nucleating agents, and the like.

[0048] However, if the chemical blowing agent composition of the present invention contains optional components, the content of organic compounds with a melting point of less than 400°C is preferably 58% by mass or less, and more preferably 22% by mass or less, based on the total amount of the chemical blowing agent composition. It is particularly preferable that the chemical blowing agent composition of the present invention does not contain organic compounds with a melting point of less than 400°C.

[0049] [Composition of chemical blowing agent composition] The chemical blowing agent composition of the present invention contains sodium bicarbonate and acidic substance A. Furthermore, it may contain any other component within the above range. The components contained in the chemical blowing agent composition of the present invention will be described below.

[0050] (Sodium bicarbonate) Sodium bicarbonate is a solid (typically powdered) chemical blowing agent at room temperature (25°C), and undergoes thermal decomposition as shown in formula (1). The decomposition of sodium bicarbonate according to formula (1) is said to begin gradually from 50°C.

[0051] In the chemical blowing agent composition of the present invention, sodium bicarbonate reacts with acidic substance A according to formula (2). In this case, since the reaction temperature is not particularly determined, bubbles can be generated simply by adding it to a thermoplastic resin or thermoplastic elastomer that mainly constitutes the foam matrix and then molding it.

[0052] (Acidic substance A) Acidic substance A is typically a solid at room temperature (25°C), and is preferably in powder form. Acidic substance A produces proton H in the presence of water or an aqueous medium. + The substance must be able to dissociate, that is, any substance whose pH (measured at a temperature of 23°C; hereafter, unless otherwise specified, "pH" refers to the pH of the aqueous solution of the substance measured at 23°C) is less than 7.0. From the viewpoint of miniaturizing bubbles when formed into a foam, the pH of acidic substance A is preferably 4.6 or less, and more preferably in the range of 2.1 to 4.6. The particle shape and average particle size of acidic substance A are preferably the same as, for example, the particle shape and average particle size of sodium bicarbonate used together.

[0053] Examples of acidic substance A1 include solid acids or acid salts such as boric acid, its anhydride, borate, phosphate, sulfite, and metal acid oxides. Among these, one or more selected from boric acid, diboron trioxide, sodium dihydrogen phosphate, and sodium bisulfite are preferred as acidic substance A.

[0054] In a chemical blowing agent composition, the ratio of sodium bicarbonate to acidic substance A is preferably such that, when the total of sodium bicarbonate and acidic substance A is 100% by mass, the sodium bicarbonate is in the range of 5 to 90% by mass and the acidic substance A is in the range of 95 to 10% by mass, from the viewpoint of easily refining the bubble size. More preferably, the sodium bicarbonate is in the range of 10 to 85% by mass and the acidic substance A is in the range of 90 to 15% by mass. Even more preferably, the sodium bicarbonate is in the range of 15 to 80% by mass and the acidic substance A is in the range of 85 to 20% by mass.

[0055] (optional ingredient) The chemical blowing agent composition may contain, as an optional component, other chemical blowing agents other than sodium bicarbonate, to the extent that it does not impair the effects of the present invention. Specific examples of other chemical blowing agents include azodicarbonamide (ADCA), P,P'-oxybis(benzenesulfonyl hydrazide) (OBSH), N,N'-dinitrosopentamethylenetetramine, 5-phenyl-1,2,3,4-tetrazole, and organic acid metal salts.

[0056] Among other chemical blowing agents, organic chemical blowing agents with a melting point of less than 400°C (hereinafter also referred to as "low-melting-point organic chemical blowing agents") are preferably included in the chemical blowing agent composition such that the total content of organic compounds with a melting point of less than 400°C (hereinafter also referred to as "low-melting-point organic compounds") is 58% by mass or less. It is more preferable that the chemical blowing agent composition does not contain low-melting-point organic chemical blowing agents, and it is particularly preferable that it does not contain other chemical blowing agents.

[0057] The chemical blowing agent composition may contain, as an optional component, other auxiliary agents other than acidic substance A, such as blowing aids other than acidic substance A, drip inhibitors, antioxidants, lubricants, dispersants, nucleating agents, etc., to the extent that it does not impair the effects of the present invention.

[0058] Other auxiliary agents include, specifically, inorganic compounds that are not acidic, such as talc, calcium carbonate, lithium carbonate, and lithium borate. Additionally, organic acidic compounds with melting points below 400°C, such as citric acid and monosodium citrate, and organic compounds that are not acidic, such as lithium stearate, lithium acetate, lithium oxalate, lithium citrate, sodium oxalate, and sodium benzoate, are also used.

[0059] Among the other auxiliary agents, organic foaming aids with a melting point of less than 400°C (hereinafter also referred to as "low-melting-point organic foaming aids") are preferably included in the chemical foaming agent composition in such a total content of low-melting-point organic compounds as 58% by mass or less. It is more preferable that the chemical foaming agent composition does not contain low-melting-point organic foaming aids, and it is particularly preferable that it does not contain other auxiliary agents.

[0060] In addition to the compounds mentioned above, compounds described later as specific examples of drip inhibitors, antioxidants, lubricants, etc., in the foaming materials can also be used as specific examples of other auxiliary agents in the chemical foaming agent composition. Even when the chemical foaming agent composition contains auxiliary agents other than these foaming aids, it is preferable that the total content of low-melting-point organic compounds in the chemical foaming agent composition is 58% by mass or less. It is more preferable that the chemical foaming agent composition does not contain low-melting-point organic compounds among the auxiliary agents other than these foaming aids, and it is particularly preferable that it does not contain any auxiliary agents other than these foaming aids.

[0061] As described above, it is preferable that the chemical blowing agent composition of the present invention does not contain any components other than sodium bicarbonate and acidic substance A. In other words, it is preferable that the chemical blowing agent composition of the present invention consists of sodium bicarbonate and acidic substance A.

[0062] [Form of chemical blowing agent composition] The chemical blowing agent composition of the present invention may be in the form of a mixture of sodium bicarbonate and acidic substance A, or a mixture of these essential components with an optional component added. The chemical blowing agent composition of the present invention may also be in the form of a two-component or multi-component type composition in which sodium bicarbonate and acidic substance A are prepared separately, or, if an optional component is used in addition to these essential components, the optional component is further prepared separately, and each of the separately prepared components is combined at the time of use.

[0063] [Chemical foaming agent masterbatch] The chemical blowing agent masterbatch of the present invention is characterized by containing the chemical blowing agent composition of the present invention and a thermoplastic resin or thermoplastic elastomer (resin, etc.).

[0064] When forming a foam using the chemical blowing agent composition of the present invention, for example, a foaming material is produced by directly blending the chemical blowing agent composition with a resin or the like that mainly constitutes the matrix of the foam, and then foaming and molding the foaming material. The foaming material may also be produced by blending the chemical blowing agent masterbatch of the present invention with a resin or the like.

[0065] By using the chemical blowing agent masterbatch of the present invention, the dispersibility of the chemical blowing agent composition in resins and other materials is improved, making uniform mixing easier. Uniform dispersion of the chemical blowing agent composition suppresses the bonding of bubbles, resulting in finer bubble sizes.

[0066] The resins contained in the chemical blowing agent masterbatch of the present invention can be part of the resins contained in the foaming material in the foam described later. In a foam molded using a chemical blowing agent masterbatch, the total of the resins derived from the chemical blowing agent masterbatch and the resins added later in the foaming material mainly constitutes the matrix of the foam.

[0067] If X [mass%] is the ratio of resins, etc. in the chemical blowing agent masterbatch to the total amount (100 mass%) of resins, etc. added later in the chemical blowing agent masterbatch, then X [mass%] is preferably 1 to 5 mass%, and more preferably 2 to 4 mass%. The content of the chemical blowing agent composition in the chemical blowing agent masterbatch of the present invention can be calculated from the content of the chemical blowing agent composition relative to the total amount of resins, etc. in the foaming material described later. If Y [mass%] is the content of the chemical blowing agent composition relative to the total amount of resins, etc. in the foaming material, then the content of the chemical blowing agent composition in the chemical blowing agent masterbatch can be Y / (X / 100) [mass%] relative to the total amount of resins, etc.

[0068] Furthermore, when multiple types of resins are used as the main components of the foam matrix, the resins in the chemical foaming agent masterbatch and the resins added later may be the same or different.

[0069] The chemical blowing agent masterbatch of the present invention may further contain other additives as needed. Specific examples of other additives include those similar to those used in the blowing materials described later.

[0070] The method for producing the chemical blowing agent masterbatch of the present invention is not particularly limited, and one example is to dry blend a resin or the like with the chemical blowing agent composition of the present invention and other additives added as needed to obtain a mixture that serves as the chemical blowing agent masterbatch.

[0071] Alternatively, the mixture obtained above may be prepared as a chemical blowing agent masterbatch by melt-kneading. During melt-kneading, the following operations may be performed to minimize the decomposition of sodium bicarbonate and the reaction between sodium bicarbonate and acidic substance A, i.e., to suppress foaming. For example, operations such as applying pressure to the molten mixture, setting a low temperature for the molten mixture, or cooling immediately after melt-kneading may be performed.

[0072] [Foam] The foam of the present invention is characterized by being foamed and molded from a foaming material containing the chemical blowing agent composition or chemical blowing agent masterbatch of the present invention and a thermoplastic resin or thermoplastic elastomer.

[0073] "Foaming material" is a composition obtained by mixing a thermoplastic resin or thermoplastic elastomer with a chemical blowing agent, a chemical blowing agent composition, or a chemical blowing masterbatch. "Foam" is a molded article obtained by foaming a composition obtained by mixing a thermoplastic resin or thermoplastic elastomer with a chemical blowing agent, a chemical blowing agent composition, or a chemical blowing agent masterbatch into a predetermined shape. It may also be said that the foaming material is foamed and molded into a predetermined shape.

[0074] The foaming material according to the present invention is a composition containing the chemical blowing agent composition or chemical blowing agent masterbatch of the present invention and a thermoplastic resin or thermoplastic elastomer. The foam of the present invention is a molded article obtained by foaming the foaming material according to the present invention into a predetermined shape.

[0075] [Foam materials] The foaming material for obtaining the foam of the present invention contains the chemical foaming agent composition or chemical foaming agent masterbatch of the present invention and a thermoplastic resin or thermoplastic elastomer (resin, etc.).

[0076] As described above, the foaming material may be manufactured by directly blending a chemical blowing agent composition with a resin or the like that mainly constitutes the matrix of the foam of the present invention, or by blending the chemical blowing agent masterbatch of the present invention with a resin or the like. When the chemical blowing agent masterbatch of the present invention is used in the foaming material, the resin or the like contained in the foaming material is the sum of the resin or the like contained in the chemical blowing agent masterbatch of the present invention and any resin or the like that added later.

[0077] The resin contained in the foaming material can be any thermoplastic resin or thermoplastic elastomer commonly used in foam molding, without any particular limitations. In other words, according to the foam of the present invention, by using the chemical blowing agent composition of the present invention, it is possible to refine the bubbles and suppress the decrease in flame retardancy due to the effects described above. Therefore, according to the foam of the present invention, by using the chemical blowing agent composition of the present invention, regardless of the type of thermoplastic resin or thermoplastic elastomer used, it is possible to refine the bubbles and suppress the decrease in flame retardancy in the same way.

[0078] As will be explained below, the thermoplastic resin or thermoplastic elastomer contained in the foaming material is not particularly limited, but it is preferable that it contains at least one selected from polyolefin resin, acrylonitrile-butadiene-styrene resin (ABS resin), polystyrene resin, polyamide resin, polyvinyl chloride resin, ethylene vinyl acetate resin, and thermoplastic elastomer.

[0079] (thermoplastic resin) Examples of thermoplastic resins include polyolefin resins, polystyrene resins, polyamide resins, polyimide resins, polyester resins, acrylic resins, polyurethane resins, polyvinyl chloride resins, vinyl acetate resins, ethylene vinyl acetate resins, epoxy resins, phenolic resins, melamine resins, polycarbonate resins, polyacetal resins, polyphenylene ether resins, polyphenylene sulfide resins, polysulfone resins, styrene-acrylonitrile resins (AS resins), styrene-(meth)acrylic acid resins, styrene-methyl methacrylate resins, acrylonitrile-butadiene-styrene resins (ABS resins), and methyl methacrylate-butadiene-styrene resins (MBS resins).

[0080] Among these, polyolefin resin, ABS resin, polystyrene resin, polyamide resin, polyvinyl chloride resin, and ethylene vinyl acetate resin are preferred as thermoplastic resins for use in the foam of the present invention.

[0081] <Polyolefin resin> Polyolefin resins are homopolymers or copolymers polymerized with olefins as the main monomer component. In this specification, "olefin" refers to an aliphatic chain unsaturated hydrocarbon having one double bond.

[0082] Here, the main component constituting the resin (polymer) refers to the component that makes up 50% by mass or more of the total monomer components constituting the polymer. Polyolefin resin is a homopolymer or copolymer containing olefin in an amount of 60 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 80 to 100% by mass of the total monomer components.

[0083] Olefin copolymers include copolymers of olefins with other olefins, or copolymers of olefins with other monomers copolymerizable to olefins. The content of the above other monomers in the polyolefin resin is preferably 30% by mass or less, more preferably 0 to 20% by mass, of the total monomer components.

[0084] As the olefin, α-olefins having 2 to 12 carbon atoms are preferred. Examples of olefins include ethylene, propylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 1-octene, and 1-decene. When polymerizing polyolefin resins, one type of olefin may be used alone, or two or more types may be used in combination.

[0085] Other monomers copolymerizable with olefins include, for example, cyclic olefins such as cyclopentene and norbornene, and dienes such as 1,4-hexadiene and 5-ethylidene-2-norbornene. Furthermore, monomers such as vinyl acetate, styrene, (meth)acrylic acid and its derivatives, vinyl ethers, maleic anhydride, carbon monoxide, and N-vinylcarbazole may also be used. These other monomers may be used individually or in combination of two or more during the polymerization of the polyolefin resin. Note that "(meth)acrylic acid" means at least one of acrylic acid and methacrylic acid.

[0086] Specific examples of polyolefin resins include polyethylene resins mainly composed of ethylene, such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE); polypropylene resins mainly composed of propylene, such as polypropylene (propylene homopolymer), ethylene-propylene copolymer, propylene-butene copolymer, ethylene-propylene-butene copolymer, and ethylene-propylene-diene copolymer; polybutene; and polypentene.

[0087] As the polyolefin resin, polyethylene resin and polypropylene resin are preferred, and polypropylene resin is more preferred. The stereoregularity of the structure derived from propylene in the polypropylene resin may be isotactic, syndiotactic, or atactic. As the polypropylene resin, polypropylene is even more preferred.

[0088] <Polystyrene resin> Polystyrene resin is a homopolymer or copolymer obtained by polymerizing styrene monomers as the main monomer component. Examples of styrene monomers include styrene, α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, and bromostyrene.

[0089] As for the polystyrene resin, a polystyrene resin having styrene as its main component, that is, a polystyrene resin containing 50% by mass or more of styrene, is preferred, and polystyrene (styrene homopolymer) is more preferred.

[0090] As the polystyrene resin, a copolymer of a styrene-based monomer as a main component and a vinyl monomer copolymerizable with this styrene-based monomer may be used. Examples of such vinyl monomers include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cetyl (meth) acrylate, (meth) acrylonitrile, dimethyl maleate, dimethyl fumarate, diethyl fumarate, ethyl fumarate, and further include bifunctional monomers such as divinylbenzene and alkylene glycol dimethacrylate.

[0091] <ABS resin> ABS resin (acrylonitrile-butadiene-styrene resin) is a thermoplastic resin having a structure in which styrene and acrylonitrile are graft-polymerized onto rubbers such as polybutadiene (BR) and styrene-butadiene copolymer (SBR).

[0092] ABS resin can also be produced by a blending method of mechanically mixing rubber and AS resin. From the viewpoint of the uniformity of product quality, the ABS resin obtained by a graft method of polymerizing styrene and acrylonitrile in the presence of rubber and a graft-blending method of mixing the polymer obtained by the graft method and AS resin is preferred.

[0093] In the ABS resin, for example, it is possible to replace a part of styrene with α-methylstyrene for the purpose of improving heat resistance. Also, in the ABS resin, it is possible to introduce methyl methacrylate into the AS resin phase.

[0094] <Polyamide resin> Examples of the polyamide resin include aliphatic, aromatic, and aliphatic-aromatic polyamide homopolymers, aliphatic and aromatic polyamide copolymers, and mixtures thereof.

[0095] Polyamide homopolymers specifically include polyhexamethylene adipamide (polyamide 66), polyhexamethylene azelaamide (polyamide 69), polyhexamethylene sebakamid (polyamide 610), polyhexamethylene dodecanediamide (polyamide 612), polytetramethylene adipamide (polyamide 46), polidodecanemethylene dodecaneamide (polyamide 1212), polycyclamide Q2 (polyamide C8), and others.

[0096] Polyamide homopolymers further include polyamides prepared by ring-opening of lactams such as polycaprolactam (polyamide 6), polylaurolactam (polyamide 12), poly-11-aminoundecanoic acid (polyamide 11), and di(p-aminocyclohexyl)methanedodecanediamide. Aromatic polyamides such as polyxylylene adipamide (polyamide MXD6), polytrimethylhexamethylene terephthalamide (polyamide 6-3-T), polyhexamethylenediamine terephthalamide (polyamide 6T), and polyhexamethylene isophthalamide (polyamide 6I) are also included.

[0097] Examples of aliphatic and aromatic polyamide copolymers include polyamides prepared by copolymerizing at least two of the above polymers or their constituent components. Specific examples of these copolymers include polyamide 6 / 66 copolymers, polyamide 6 / 12 copolymers, polyamide 6 / 6T copolymers, and polyamide 6I / 6T copolymers.

[0098] The thermoplastic resin used in the foam of the present invention may be one of the thermoplastic resins listed above, or two or more may be used in combination. For example, polystyrene resin may be used as the main component, and polystyrene resin may be used in combination with other resins. In that case, polyethylene resin, polypropylene resin, acrylic resin, AS resin, ABS resin, etc. are preferred as the other resins.

[0099] (Thermoplastic elastomer) Thermoplastic elastomers are polymers or polymer blends that have properties similar to vulcanized rubber at the operating temperature, but can be molded and remolded like thermoplastic resins when heated. In the present invention, thermoplastic elastomers are preferred as resins, similar to the polyolefin resins, ABS resins, polystyrene resins, polyamide resins, polyvinyl chloride resins, and ethylene vinyl acetate resins mentioned above as thermoplastic resins.

[0100] Thermoplastic elastomers contain both a flexible component (rubber phase or soft segment) and a molecularly restricting component (resin phase or hard segment) within the material. The soft segment can utilize the chemical composition and structure of various raw rubber materials, while the hard segment can employ various resin components. Thermoplastic elastomers are generally classified according to the chemical composition of the hard segment.

[0101] Examples of thermoplastic elastomers classified in this way include styrene elastomers, chlorinated polyethylene, PVC elastomers, olefin elastomers, urethane elastomers, ester elastomers, amide elastomers, and ionomers.

[0102] Examples of styrene-based elastomers include block copolymers of styrene and butadiene or isoprene (SBS or SIS) and their hydrogenated polymers (SEBS or SEPS). Furthermore, styrene-based elastomers include high-impact polystyrene (HIPS), which is obtained by adding diene-based rubbery polymers such as polybutadiene (BR), styrene-butadiene copolymer (SBR), and ethylene-propylene-non-conjugated diene three-dimensional copolymer to polystyrene resin.

[0103] Examples of PVC-based elastomers include blends of high-polymerization polyvinyl chloride (PVC) and plasticizers, blends of partially crosslinked PVC (in which a crosslinked structure is imparted during PVC synthesis) and plasticized PVC, and blends of PVC with acrylonitrile-butadiene rubber (NBR) or urethane rubber.

[0104] Examples of olefin-based elastomers include simple blends of polyolefins, preferably polypropylene, with rubber, such as ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), isobutylene-isoprene rubber (IIR), natural rubber (NR), NBR, etc., and dynamic vulcanization types in which the rubber is vulcanized when mixing the polyolefin and rubber to finely disperse crosslinked rubber particles in the polyolefin.

[0105] For urethane-based elastomers, block copolymers in which the hard segment is polyurethane and the soft segment is an aliphatic polyether or polyester can be applied. For ester-based elastomers, block copolymers in which the hard segment is aromatic polyester and the soft segment is an aliphatic polyether or polyester can be applied. For amide-based elastomers, block copolymers in which the hard segment is an aliphatic polyamide (mainly polyamide 12 and 11) and the soft segment is an aliphatic polyether or polyester can be applied.

[0106] The thermoplastic resin or thermoplastic elastomer contained in the foaming material of the present invention may be one selected from the above thermoplastic resins and thermoplastic elastomers used alone, or two or more may be used in combination.

[0107] (Composition of foaming material) The foaming material according to the present invention preferably contains the chemical foaming agent composition of the present invention in an amount of 0.1 to 1.7% by mass, and more preferably in an amount of 0.2 to 0.5% by mass, relative to the total amount of thermoplastic resin and thermoplastic elastomer (resin, etc.) in the foaming material.

[0108] Furthermore, the proportion of organic compounds with a melting point of less than 400°C derived from the chemical blowing agent composition, relative to the total amount of the foaming material, is preferably within the range of 1% by mass or less, more preferably 0.3% by mass or less, and particularly preferably 0% by mass, i.e., not contained.

[0109] As a result, the content of organic compounds with a melting point of less than 400°C derived from the chemical blowing agent composition in the foam of the present invention obtained using the above-mentioned foaming material can be reduced to 1% by mass or less, more specifically to 0.3% by mass or less, and in particular to 0% by mass. Furthermore, as a result, in the foam of the present invention obtained using the above-mentioned foaming material, the decrease in flame retardancy that occurs when a foam is made using a chemical blowing agent composition, compared to when a resin or the like does not contain a chemical blowing agent composition, can be suppressed.

[0110] The foamed material according to the present invention preferably contains a flame retardant as an optional component, depending on the type of thermoplastic resin or thermoplastic elastomer. Whether or not to add a flame retardant to the foamed material is appropriately selected, for example, in the flame retardancy evaluation described later, using the burning time of the resin, etc., as an indicator. Examples of resins, etc., that have flame retardancy without the addition of a flame retardant include polyamide resins.

[0111] (Flame retardant) Examples of flame retardants include brominated flame retardants, phosphorus-based flame retardants, and inorganic flame retardants such as antimony compounds and metal hydroxides. Flame retardants may be used individually or in combination of two or more types.

[0112] <Bromine-based flame retardant> Examples of brominated flame retardants include tetrabromobisphenol A (TBBA), decabromodiphenyl ether (Deca-BDE), tribromophenol, hexabromocyclododecane (HBCD), ethylenebis(tetrabromophthalimide), TBBA carbonate oligomer, TBBA epoxy oligomer, brominated polystyrene, bis(pentabromophenyl)ethane, TBBA-bis(dibromopropyl ether), poly(dibromophenol), and hexabromobenzene (HBB).

[0113] As brominated flame retardants, bis(hydroxyphenyl)sulfone derivatives, bis(alkoxyphenyl)sulfone derivatives, etc., may be used. Specifically, examples include bis[3,5-dibromo-4-(2,3-dibromopropoxy)phenyl]sulfone.

[0114] Among brominated flame retardants, non-drip type brominated flame retardants that prevent the dripping (drip) of resins, etc., during combustion include, for example, bis(pentabromophenyl)ethane. When using drip-type brominated flame retardants, drip inhibitors described later may be used in combination.

[0115] <Phosphorus-based flame retardant> The phosphorus-based flame retardant may be either an organophosphorus-based or an inorganic phosphorus-based flame retardant. Examples of organophosphorus-based flame retardants include organic phosphate esters. Examples of organic phosphate esters include phosphate ester compounds such as phosphite esters, phosphate esters, and phosphonic acid esters, and among these, the use of phosphate esters is particularly preferred. In the case of inorganic phosphorus-based flame retardants, high molecular weight inorganic phosphorus compounds are preferred, such as ammonium polyphosphate and its derivatives.

[0116] Specific examples of phosphite esters include triphenyl phosphite, tris(nonylphenyl) phosphite, tris(2,4-di-t-butylphenyl) phosphite, distearyl pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, and bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite.

[0117] Specific examples of phosphate esters include triphenyl phosphate, tris(nonylphenyl) phosphate, tris(2,4-di-t-butylphenyl) phosphate, distearyl pentaerythritol diphosphate, bis(2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphate, bis(2,4-di-t-butylphenyl) pentaerythritol diphosphate, tributyl phosphate, bisphenol A bis-diphenyl phosphate, and aromatic condensed phosphate esters.

[0118] Examples of aromatic condensed phosphate esters include 1,3-phenylenebis(di2,6-xylenyl phosphate), bisphenol A bis(diphenyl phosphate), and 1,3-phenylenebis(diphenyl phosphate).

[0119] Specific examples of phosphonic acid esters include dimethyl benzenephosphonate and benzenephosphonic acid esters.

[0120] The flame retardant content in the foamed material according to the present invention is preferably in the range of 1 to 30% by mass relative to the total amount of resin, etc. If the flame retardant content in the foamed material is within the above range, the resulting foam will have good flame retardancy and foam moldability will be easily ensured. The flame retardant content is more preferably in the range of 1 to 25% by mass relative to the total amount of resin, etc.

[0121] (Other additives) The foaming material according to the present invention contains a resin and the chemical foaming agent composition of the present invention as essential components, and further contains a flame retardant as an optional component. The foaming material according to the present invention may contain other additives other than the flame retardant, to the extent that it does not impair the effects of the present invention. Other additives that can be applied are known additives that are commonly added to foams. Examples of other additives include drip inhibitors, antioxidants, lubricants, hindered amine compounds, ultraviolet absorbers, antistatic agents, fluorescent whitening agents, pigments, dyes, etc.

[0122] <Drip prevention agent> Drip inhibitors are added to prevent the dripping (drip) of resin material during combustion and to improve flame retardancy. Examples of drip inhibitors include fluorine-based drip inhibitors, silicone rubbers, and layered silicates. Drip inhibitors may be used individually or in combination of two or more types.

[0123] <Antioxidant> Examples of antioxidants include hindered phenol antioxidants, phosphite ester antioxidants, or mixtures thereof.

[0124] <Lubricant> Examples of lubricants include one or more selected from the group consisting of fatty acid salts, fatty acid amides, silane polymers, solid paraffin, liquid paraffin, calcium stearate, zinc stearate, stearic acid amide, silicone powder, methylenebisstearate, and N,N'-ethylenebisstearate.

[0125] The content of other additives in the foaming material according to the present invention is within a range that does not impair the effects of the present invention, for example, in a total range of about 0.1 to 58% by mass relative to the total amount of foaming material, and preferably in a total range of 0.1 to 22.5% by mass.

[0126] The foaming material according to the present invention is obtained by appropriately mixing the above-mentioned components. Specifically, a method is used in which a mixture obtained by dry blending a resin, the chemical foaming agent composition of the present invention, an optionally contained flame retardant, and other additives that may be contained as needed is used as the foaming material.

[0127] Furthermore, in the preparation of the foaming material, the chemical blowing agent masterbatch of the present invention may be used instead of the chemical blowing agent composition of the present invention. That is, a mixture obtained by dry blending a resin, etc., the chemical blowing agent masterbatch of the present invention, an optionally contained flame retardant, and other additives which may be contained as needed may be used as the foaming material. When a chemical blowing agent masterbatch is used in the preparation of the foaming material, the content of the resin, etc. in the foaming material is the sum of the amount of the resin, etc. in the chemical blowing agent masterbatch and the amount of the resin, etc. added separately.

[0128] Alternatively, the mixture obtained above may be used as a foaming material by melt-kneading. During melt-kneading, the following operations may be performed to minimize the decomposition of sodium bicarbonate and the reaction between sodium bicarbonate and acidic substance A, i.e., to suppress foaming. For example, operations such as applying pressure to the molten mixture, setting a low temperature for the molten mixture, or cooling immediately after melt-kneading.

[0129] Furthermore, the foaming material according to the present invention can take various forms, such as powder, granules, tablets, pellets, flakes, fibers, and liquid, depending on the preparation method described above.

[0130] [Foam] The foam of the present invention is obtained by foam molding the above-mentioned foam material. The foam molding method is not particularly limited, and known foam molding methods using sodium bicarbonate as a chemical foaming agent can be applied. Specifically, the foam is obtained by molding the above-mentioned foam material and heating it to a temperature above the decomposition temperature of sodium bicarbonate. The preferred foam molding method for obtaining the foam of the present invention is the manufacturing method of the present invention, which will be described later.

[0131] The foam of the present invention is a foam in which the diameter of the air bubbles is fine and the reduction in flame retardancy is suppressed.

[0132] The bubble diameter in the foam of the present invention is preferably 0.4 mm or less, and more preferably 0.2 mm or less, as an average bubble diameter measured by, for example, the following method.

[0133] <Method for measuring bubble diameter> The foam is cut with a cutter or the like, and the cross-section is observed using a transmission electron microscope, such as the JEM-2000FX (manufactured by JEOL Ltd.), to capture an image of the foamed area. Here, the foamed area refers to the region near the center of the cross-section where uniform bubbles can be observed, excluding the dense skin layer and the area near the skin layer where the bubble morphology is clearly different from the foamed area, which has a dense skin layer with virtually no bubbles and uniform bubbles, when the foam is molded in a mold.

[0134] In the cross-section of the foamed section described above, the maximum diameter of all bubbles present in a randomly selected 2mm x 8mm measurement area is measured using an image measuring device (NEXIV VMR3020), and the average is calculated as the average bubble diameter.

[0135] Furthermore, the flame retardancy of the foam of the present invention can be evaluated, for example, using the burning time measured in the following combustion test as an indicator. Specifically, in the above foam material, if the burning time when a molded body made from a molding material that does not contain the chemical blowing agent composition of the present invention is subjected to the following combustion test is denoted as T1, and the burning time when the foam of the present invention is subjected to the following combustion test is denoted as T2, it is preferable that T2 does not increase significantly compared to T1.

[0136] Regarding the relationship between T2 and T1, for example, it is preferable that T2 / T1 be 2.0 or less, and more preferably 1.5 or less. Specifically, considering the criteria of ASTM D3801, T2 is preferably 30 seconds or less, and more preferably 10 seconds or less.

[0137] <Burning time> The burning time will be measured using a 20mm vertical combustion test in accordance with ASTM D3801. Three test specimens will be prepared, each measuring 125±5mm × 13±0.5mm with a thickness of 2mm. Each test specimen will be mounted vertically in a clamp, and a 20mm flame will be applied to the lower end of the specimen twice for 10 seconds each using a burner. The combustion behavior will be used to make a determination.

[0138] The burning time was determined by the following method: For each test specimen, the longer of the two flammable burning times during flame contact was adopted as the burning time. The average of these burning times across three test specimens was then used as the burning time.

[0139] (Application) The applications of the foam of the present invention are not particularly limited, and include, for example, electrical and electronic components, electrical components, exterior and interior components in fields such as home appliances and automobiles, as well as various packaging materials, household goods, office supplies, piping, and agricultural materials.

[0140] [Method for manufacturing foam] The present invention provides a method for producing foam, characterized by comprising the following steps: (1) a foaming material preparation step and (2) a foaming molding step.

[0141] (1) A step of obtaining a foaming material by mixing the chemical foaming agent composition or the chemical foaming agent masterbatch of the present invention with a thermoplastic resin or thermoplastic elastomer (resin, etc.) (foaming material preparation step) (2) A step of foaming the foam material obtained in (1) above using an injection molding machine (foaming process)

[0142] The manufacturing method of the present invention may include steps other than (1) the foam material preparation step and (2) the foam molding step, as needed. Each step will be described below.

[0143] [Foam material preparation process] The foam material preparation step in the manufacturing method of the present invention can be carried out in the same manner as the foam material preparation method described above for the foam. The content of each component in the foam material can also be the same as the content of each component in the foam material described above for the foam.

[0144] Specifically, one method involves dry-blending a mixture of a resin, the chemical blowing agent composition of the present invention, an optionally included flame retardant, and other additives that may be included as needed, to obtain a foaming material. Alternatively, in the above, the foaming material may be prepared using the chemical blowing agent masterbatch of the present invention instead of the chemical blowing agent composition of the present invention. When using the chemical blowing agent masterbatch to prepare the foaming material, the content of the resin, etc. in the foaming material is the sum of the amount of the resin, etc. in the chemical blowing agent masterbatch and the amount of the resin, etc. added separately.

[0145] Alternatively, foaming materials may be prepared by melt-mixing. During melt-mixing, the following operations may be performed to minimize the decomposition of sodium bicarbonate and the reaction between sodium bicarbonate and acidic substance A, i.e., to suppress foaming: for example, applying pressure to the molten mixture, setting a low temperature for the molten mixture, or cooling immediately after melt-mixing.

[0146] One method of dry blending involves mixing each component of the foaming material using various mixing machines, such as tumblers or high-speed mixers known as Henschel mixers.

[0147] Melt mixing is generally carried out using mixing equipment such as Banbury mixers, rolls, plastographs, extruders (single-screw extruders, multi-screw extruders (e.g., twin-screw extruders), etc.), and kneaders. Among these, melt mixing is preferably carried out using an extruder because it offers good production efficiency. Furthermore, since it is possible to impart high shear strength, it is preferable to use a multi-screw extruder for melt mixing, and even more preferable to use a twin-screw extruder. Here, the term extruder is used in a category that includes extruder mixers.

[0148] The temperature and pressure during melt mixing should be set to minimize the decomposition of sodium bicarbonate and the reaction between sodium bicarbonate and acidic substance A. When an extruder is used for melt mixing, the mixing melt temperature corresponds to the cylinder temperature.

[0149] When using an extruder for melt mixing, the screw rotation speed is preferably in the range of 50 to 300 rpm. Furthermore, the discharge rate of the foaming material from the extruder is preferably in the range of 1 to 50 kg / hr.

[0150] In the foam material preparation process, the kneaded material can be extruded into strands, and then processed into pellets, flakes, or other forms.

[0151] [Foam molding process] The foam molding step in the manufacturing method of the present invention is a step of foam molding the foam material obtained above using an injection molding machine.

[0152] As an injection molding machine, for example, a general injection molding machine can be used that includes a cylinder for heating foam material, an injection unit connected to the cylinder for injecting the heated foam material from the cylinder, and a mold for shaping the injected foam material into a predetermined form.

[0153] The heating of the foaming material inside the cylinder is set to a temperature at which the foaming material reaches a state (viscosity) that allows it to be injected from the injection nozzle. This heating temperature is, for example, above the melting temperature of the resin contained in the foaming material. When polypropylene resin is used as the resin, the heating temperature of the foaming material is preferably in the range of 190 to 220°C, and more preferably in the range of 200 to 210°C. When ABS resin is used as the resin, the heating temperature of the foaming material is preferably in the range of 220 to 240°C. The temperature of the foaming material inside the cylinder can be treated as approximately the same as the temperature of the cylinder. Even if the temperature of the foaming material inside the cylinder filled with the foaming material exceeds the decomposition temperature of sodium bicarbonate, foaming will not occur because the foaming material cannot increase in volume under sealed conditions.

[0154] The injection conditions are adjusted as appropriate according to the structure of the injection molding machine, particularly the structure of the injection section. The injection pressure is the pressure required to inject the heated foam material from the cylinder into the mold cavity, and can generally be in the range of 10 to 200 MPa. The injection time, i.e., the time from the start to the end of injection, is preferably, for example, within 2 seconds. The injection speed is adjusted as appropriate according to, for example, the type of resin used, the product shape, the product thickness, etc.

[0155] During injection molding, if the injection time exceeds the above upper limit, crystallization of the resin may occur, making it difficult to increase the foaming ratio, and allowing the foaming gas in the matrix to escape to the surface, which may cause silver marks or other defects to appear on the surface of the molded foam.

[0156] The foam material injected into the mold cavity is foamed and molded to the shape of the cavity. The volume of the mold cavity used is set to be larger than the volume of the raw foam material, and the foam material injected by injection foams within the mold cavity, filling the entire cavity with foam. The foaming ratio is obtained by dividing the volume of the mold cavity by the volume of the foam material used.

[0157] The temperature of the foaming material during foam molding is above the decomposition temperature of sodium bicarbonate, preferably in the range of 170 to 230°C. The temperature of the foaming material during foam molding may also be estimated, for example, by the temperature of the foaming material during injection, i.e., the temperature of the cylinder.

[0158] The mold may be one with a fixed cavity volume, or it may be one with a variable cavity volume. When using a mold with a variable cavity volume, the volume can be kept small when filling with the foaming material, and then expanded after filling to actively promote bubble generation and expansion. This molding method is called core-back molding. With core-back molding, a skin layer is formed when the foaming material comes into contact with the mold, resulting in a foam with a good surface appearance.

[0159] As for the conditions for core-back molding, from the viewpoint of achieving uniform foaming, it is preferable to keep the time from the completion of filling the cavity with foaming material to the start of cavity volume expansion short, for example, within 2 seconds.

[0160] Furthermore, it is preferable to cool the resulting foam by cooling the mold after foam molding. If the injection time is short, the mold temperature can be set to the cooling temperature from the time the foam material is injected. The cooling temperature (mold and foam temperature) is preferably, for example, 40-80°C. The cooling time is adjusted appropriately depending on, for example, the type of resin used, the product shape, the product thickness, etc. After cooling, the foam is removed from the mold, completing the foam manufacturing process. [Examples]

[0161] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the examples, the units "parts" or "%" are used, and unless otherwise specified, they refer to "parts by mass" or "mass%".

[0162] [Preparation of chemical blowing agent compositions] Chemical blowing agent compositions 10-13 of the present invention and comparative chemical blowing agent compositions 1-9 and 14-15 were prepared by mixing 1 part by mass each of the compounds shown in Table I with 0.2 parts by mass of sodium bicarbonate. Table I shows the melting point of the compound, the pH when the compound is dissolved in water, and whether the compound is an organic or inorganic compound. In addition, Table I also shows the content of organic compounds with a melting point of less than 400°C in the chemical blowing agent composition as content B [mass%].

[0163] <Rating> Foaming material 1 was prepared by weighing 100 parts by mass of polypropylene (Novatec PP_MG03BD (product name, manufactured by Nippon Polypropylene Co., Ltd.) as a resin, 5 parts by mass of bis[3,5-dibromo-4-(2,3-dibromopropoxy)phenyl]sulfone as a flame retardant, and 1.2 parts by mass of the above chemical blowing agent composition 1, and manually mixing them. Foaming materials 2 to 15 were prepared in the same manner, containing chemical blowing agent compositions 2 to 15 instead of chemical blowing agent composition 1.

[0164] For foam materials 1 to 15, foams with a foaming ratio of 1.1 times (the size of the foam was the same as the test piece used for burning time measurement) were molded using an injection molding machine (ROBOSHOT 2000i 50B, manufactured by FANUC) under the following injection molding condition 1. The cylinder temperature corresponds to the temperature of the foam material inside the cylinder and during injection. A mold with a fixed volume was used. No pressure was applied to the mold during foam molding. The mold temperature corresponds to the cooling temperature.

[0165] (Injection molding conditions 1) Cylinder temperature (foaming material temperature): 200℃ Injection pressure: 20 MPa Ejection time (time from start to finish of injection): 0.9 seconds Injection speed: 40[mm / s] Mold temperature: 50℃ Cooling time: 15 seconds

[0166] The bubble diameter and burning time (T2) of the obtained foam were measured using the method described above. In addition, a resin composition without chemical blowing agent composition 1 was prepared using foam material 1, and the burning time (T1) of the molded article obtained by injection molding was measured to be 4.9 [sec]. Table I shows the bubble diameter and burning time (T2), along with T2 / T1 and T2-T1.

[0167] Figure 1 also shows a graph illustrating the relationship between the pH of the compound used in combination with sodium bicarbonate (measured at 23°C) and the bubble diameter of the resulting foam.

[0168] [Table 1]

[0169] Table I and Figure 1 show that when an acidic substance with a pH of less than 7 (Condition 1) is used together with sodium bicarbonate, the resulting foam can have fine bubbles. Furthermore, it can be seen that when the compound used together with sodium bicarbonate is an inorganic compound or an organic compound with a melting point of 400°C or higher (Condition 2), the decrease in flame retardancy is suppressed. Chemical blowing agent compositions 10 to 13, which contain a compound satisfying Conditions 1 and 2 together with sodium bicarbonate as acidic substance A, achieve the effects of the present invention, which are to achieve both fine bubbles and suppression of the decrease in flame retardancy.

[0170] [Foam manufacturing] (1) Preparation of foaming material Using the chemical blowing agent compositions 10-13 obtained above, along with the following thermoplastic resins and flame retardants, foaming materials 21-29 shown in Table II were prepared. As comparative examples, foaming materials 30-32 were prepared using only sodium bicarbonate instead of chemical blowing agent compositions 10-13, and foaming materials 33-35 (compositions shown in Table II) were prepared using chemical blowing agent composition 3 consisting of sodium bicarbonate and monosodium citrate (outside the range of acidic substance A) instead of chemical blowing agent compositions 10-13.

[0171] (thermoplastic resin) Polypropylene; Novatec PP_MG03BD (product name, manufactured by Nippon Polypropylene Co., Ltd., hereinafter referred to as "PP"). ABS resin; Sebian V_660SF (product name, manufactured by Daicel Polymer Co., Ltd., hereinafter referred to as "ABS"). Polyamide resin; Amiran CM1017 (product name, manufactured by Toray Industries, Inc., hereinafter referred to as "PA").

[0172] (Flame retardant) Bis[3,5-dibromo-4-(2,3-dibromopropoxy)phenyl]sulfone (hereinafter referred to as "flame retardant 1") Bis(pentabromophenyl)ethane (hereinafter referred to as "flame retardant 2") Condensed phosphate ester (PX-200 (product name, manufactured by Daihachi Chemical Industry Co., Ltd., hereinafter referred to as "flame retardant 3"))

[0173] [Table 2]

[0174] (2) Manufacturing of foam Using the foam materials 21-35 obtained above, foam bodies 21-35 (the size of the foam bodies being the same as the test pieces used for burning time measurement) with a foaming ratio of 1.1 were molded using an injection molding machine (ROBOSHOT_2000i_50B (product name, manufactured by FANUC)) under the injection molding conditions 1 above when using PP as the thermoplastic resin, injection molding conditions 2 below when using ABS, and injection molding conditions 3 below when using PA. The cylinder temperature corresponds to the temperature of the foam material inside the cylinder and during injection. A mold with a fixed volume was used. No pressure was applied to the mold during foam molding. The mold temperature corresponds to the cooling temperature.

[0175] (Injection molding conditions 2) Cylinder temperature (foaming material temperature): 220℃ Injection pressure: 20 MPa Ejection time (time from start to finish of injection): 0.9 seconds Injection speed: 40[mm / s] Mold temperature: 50℃ Cooling time: 15 seconds

[0176] (Injection molding conditions 3) Cylinder temperature (foaming material temperature): 250℃ Injection pressure: 20 MPa Ejection time (time from start to finish of injection): 0.9 seconds Injection speed: 40[mm / s] Mold temperature: 70℃ Cooling time: 15 seconds

[0177] The bubble diameter and burning time (T2) of the obtained foams were measured using the method described above. In addition, for each foaming material, a resin composition that did not contain a chemical blowing agent composition or sodium bicarbonate was prepared, and the burning time (T1) of the molded articles obtained by injection molding was measured. Table III shows the bubble diameter, burning time (T2), burning time (T1), as well as T2 / T1 and T2-T1.

[0178] [Table 3]

[0179] Table III shows that the foam of the present invention achieves the effect of the present invention, which is to simultaneously achieve finer pore size and suppression of flame retardancy reduction. In Table III, the term "invention" in the remarks column for foam numbers 21 and 22 should be read as "reference example". [Industrial applicability]

[0180] According to the present invention, it is possible to provide a chemical blowing agent composition and a chemical blowing agent masterbatch that can achieve both miniaturization of bubbles and suppression of flame retardancy reduction when used in the molding of a foam. Furthermore, it is possible to provide a foam produced using the above chemical blowing agent composition or chemical blowing agent masterbatch that achieves both miniaturization of bubbles and suppression of flame retardancy reduction, as well as a method for producing the same.

Claims

1. A chemical blowing agent composition containing sodium bicarbonate and an acidic substance, The acidic substance is at least one selected from sodium dihydrogen phosphate and sodium bisulfite. A chemical blowing agent composition in which, when the total of the sodium bicarbonate and the acidic substance is 100% by mass, the amount of sodium bicarbonate is in the range of 10 to 20% by mass, and the amount of the acidic substance is in the range of 90 to 80% by mass.

2. The chemical blowing agent composition according to claim 1, wherein the total amount of the chemical blowing agent composition contains an organic compound having a melting point of less than 400°C in an amount of 58% by mass or less.

3. A chemical blowing agent masterbatch containing the chemical blowing agent composition according to claim 1 or claim 2 and a thermoplastic resin or thermoplastic elastomer.

4. A foam obtained by foam molding a foaming material containing the chemical blowing agent composition according to claim 1 or claim 2 or the chemical blowing agent masterbatch according to claim 3, and a thermoplastic resin or thermoplastic elastomer.

5. The foam according to claim 4, wherein the content ratio of the organic compound derived from the chemical blowing agent composition having a melting point of less than 400°C, relative to the total amount of the foam, is within the range of 1% by mass or less.

6. The foam according to claim 4 or claim 5, wherein the thermoplastic resin or thermoplastic elastomer comprises at least one selected from polyolefin resin, acrylonitrile-butadiene-styrene resin, polystyrene resin, polyamide resin, polyvinyl chloride resin, ethylene vinyl acetate resin, and thermoplastic elastomer.

7. Furthermore, the foam according to any one of claims 4 to 6, which contains a flame retardant.

8. A step of obtaining a foamed material by mixing the chemical foaming agent composition according to claim 1 or claim 2 or the chemical foaming agent masterbatch according to claim 3 with a thermoplastic resin or thermoplastic elastomer, The process involves foaming the aforementioned foam material using an injection molding machine, A method for producing a foam having the following characteristics.

9. The method for producing a foam according to claim 8, wherein the ratio of the chemical blowing agent composition to the total amount of the thermoplastic resin or thermoplastic elastomer in the foaming material is in the range of 0.1 to 1.7% by mass.

Images