Foam, method for producing foam, and composition

Abstract

The present invention provides: a foam containing a polyamide containing a xylylenediamine unit, and an inorganic filler; a method for producing the foam; and a composition containing a polyamide containing a xylylenediamine unit, an inorganic filler, and a foaming agent.

Description

Foam, Method for Producing Foam, and Composition

[0001] The present invention relates to a foam, a method for producing the foam, and a composition.

[0002] In a molded body using a resin, foam molding is performed for the purpose of weight reduction or the like to obtain a foam. By making it a foam, the density can be lowered, a large volume can be obtained while being lightweight, and it is used for the purpose of weight reduction of products and as a cushioning material. In addition, since polyamide resins are excellent in various performances, they are applied in various fields. For example, Patent Document 1 discloses an aromatic polyamide resin composition containing an aromatic polyamide resin and a polyfunctional compound, the aromatic polyamide resin composition having a melt tension of 60 to 500 mN when measured at the melting point of the aromatic polyamide resin composition + 20°C, and a foam obtained by foaming the above composition.

[0003] Japanese Patent Application Laid-Open No. 2011-256290

[0004] Here, in a foam, it is required that the flexural modulus be easily maintained (excellent in the maintenance rate) before and after foaming. For example, a foamed molded body using a conventional polyamide such as nylon 6 has a problem that the maintenance rate of the flexural modulus before and after foaming is low, and the applicable uses are limited.

[0005] An object of the present invention is to provide a foam excellent in the maintenance rate of the flexural modulus before and after foaming, a method for producing the foam, and a composition that can be used for producing the foam.

[0006] The following are specific examples of typical embodiments of the present invention: <1> A foam comprising a polyamide containing xylylenediamine units and an inorganic filler. <2> The foam according to <1>, wherein the inorganic filler comprises glass fibers. <3> The foam according to <1> or <2>, wherein the xylylenediamine is metaxylylenediamine, paraxylylenediamine, or a mixture thereof. <4> The foam according to any one of <1> to <3>, wherein the polyamide contains α,ω-linear aliphatic dicarboxylic acid units having 4 to 20 carbon atoms as dicarboxylic acid units. <5> The foam according to <4>, wherein the α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms comprises sebacic acid. <6> The foam according to any one of <1> to <5>, wherein the foaming ratio is 1.3 to 3.0 times. <7> The foam according to any one of <1> to <6>, comprising two or more types of polyamide. <8> A method for producing a foam according to any one of <1> to <7>, comprising: preparing a foaming material comprising a polyamide containing xylylenediamine units, an inorganic filler, and a blowing agent; and foaming the foaming material. <9> The method for producing a foam according to <8>, wherein the blowing agent is a chemical blowing agent. <10> The method for producing a foam according to <8> or <9>, wherein preparing the foaming material comprises mixing at least a polyamide containing xylylenediamine units, an inorganic filler, and a blowing agent. <11> The method for producing a foam according to any one of <8> to <10>, wherein foaming the material comprises filling the cavity of a mold with the foaming material by injection. <12> The method for producing a foam according to <11>, further comprising increasing the cavity volume of the mold after filling. <13> A composition comprising a polyamide containing xylylenediamine units, an inorganic filler, and a blowing agent.

[0007] The present invention provides a foam that exhibits excellent retention of the flexural modulus before and after foaming, a method for manufacturing the foam, and a composition that can be used in manufacturing the foam.

[0008] Hereinafter, embodiments for carrying out the present invention (hereinafter simply referred to as "these embodiments") will be described in detail. These embodiments are illustrative examples for explaining the present invention, and the present invention is not limited to these embodiments. In this specification, "~" is used to include the numerical values ​​before and after it as the lower and upper limits, respectively. In this specification, all physical properties and characteristic values ​​are given at 23°C unless otherwise specified. In this specification, preferred combinations of embodiments are more preferred embodiments.

[0009] In this specification, unless otherwise specified, the number-average molecular weight shall be the value measured by the following method. The number-average molecular weight (Mn) shall be determined from the value converted to standard polymethyl methacrylate (PMMA) by gel permeation chromatography (GPC). Two columns packed with styrene polymer as the packing material shall be used, and hexafluoroisopropanol (HFIP) with a sodium trifluoroacetate concentration of 2 mmol / L shall be used as the solvent, with a resin concentration of 0.02% by mass, a column temperature of 40°C, a flow rate of 0.3 mL / min, and measurement shall be performed using a refractive index detector (RI). A calibration curve shall be obtained by dissolving six levels of PMMA in HFIP and measuring the values.

[0010] In this specification, unless otherwise specified, the melting point (Tm) shall be the value measured according to differential scanning calorimetry (DSC) in accordance with ISO 11357. Using a differential scanning calorimeter, the resin is placed in the measurement pan of the differential scanning calorimeter, heated to a temperature above the melting point at a heating rate of 10°C / min under a nitrogen atmosphere, and then rapidly cooled before measurement. The measurement conditions are as follows: heating at a heating rate of 10°C / min, held at 280°C for 5 minutes, and then cooled to 100°C at a cooling rate of -5°C / min to determine the melting point (Tm). As the differential scanning calorimeter used, Shimadzu Corporation's "DSC-60" is used. In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as the intended function of the process is achieved. All steps described herein may be performed in any preferred order, unless otherwise specified herein or unless the context clearly indicates otherwise. If measurement methods, etc., described in the standards shown herein differ from year to year, unless otherwise specified, the standards as of January 1, 2024 shall apply.

[0011] (Foam) The foam of this embodiment contains a polyamide containing xylylenediamine units and an inorganic filler. The inventors have found that by adopting this specific configuration, the retention rate of flexural strength before and after foaming is excellent. The reason for obtaining the above effect is unknown, but it is presumed to be as follows. The polyamide in the present invention is thought to have a slower crystallization rate compared to conventional nylon 6, etc., because it contains xylylenediamine units. Therefore, the crystallization rate during the production of the foam is slow, and bubbles are more easily formed in a shape that maintains the strength of the inorganic filler during foaming, resulting in excellent retention of flexural modulus. Furthermore, for the same reason, it is also excellent in terms of retention of flexural strength, and because the crystallization rate is slow, bubbles are easily formed during foaming, and even when the foaming ratio is large, bubbles are more likely to be formed in a state where cracks do not occur in the cross-section.

[0012] The details of the foam of this embodiment will be described below. Furthermore, polyamides containing xylylenediamine units are also referred to as "specific polyamides."

[0013] <Specific Polyamide> The foam of this embodiment contains a polyamide (specific polyamide) containing xylylenediamine units. In this specification, constituent units derived from xylylenediamine are referred to as xylylenediamine units, constituent units derived from diamine are referred to as diamine units, constituent units derived from dicarboxylic acids are referred to as dicarboxylic acid units, and so on.

[0014] The specific polyamide preferably contains constituent units derived from diamines (diamine units) and constituent units derived from dicarboxylic acids (dicarboxylic acid units).

[0015] The content of xylylenediamine units in the total diamine units of a particular polyamide is preferably 70 mol% or more, more preferably 75 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and particularly preferably 99 mol% or more.

[0016] The xylylenediamine in the xylylenediamine unit is preferably metaxylylenediamine, paraxylylenediamine, or a mixture thereof. The mixture preferably contains 0 to 100 mol% metaxylylenediamine and 100 to 0 mol% paraxylylenediamine (provided that the total of metaxylylenediamine and paraxylylenediamine does not exceed 100 mol%), more preferably 10 to 100 mol% metaxylylenediamine and 90 to 0 mol% paraxylylenediamine, even more preferably 10 to 90 mol% metaxylylenediamine and 90 to 10 mol% paraxylylenediamine, even more preferably 40 to 90 mol% metaxylylenediamine and 60 to 10 mol% paraxylylenediamine, and even more preferably 60 to 90 mol% metaxylylenediamine and 40 to 10 mol% paraxylylenediamine.

[0017] In the specific polyamide, it is preferable that the total of paraxylylenediamine units and metaxylylenediamine units constitutes preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, even more preferably 98 mol% or more, and even more preferably 99 mol% or more of the diamine units. The upper limit of the total of the paraxylylenediamine units and metaxylylenediamine units is 100 mol%. By setting the proportion of metaxylylenediamine to 10 mol% or more, the appearance of the surface of the test piece tends to improve when injection molded under low mold temperature conditions. Furthermore, by setting the proportion of metaxylylenediamine to 10 mol% or more, the crystallization rate is slowed, which allows sufficient time for inorganic fillers such as glass fibers to orient properly, and thus the flexural modulus after foaming is thought to increase. In addition, by setting the proportion of paraxylylenediamine to 10 mol% or more, crystallization can be promoted at a lower mold temperature.

[0018] Diamines other than metaxylylenediamine and paraxylylenediamine that can be used as raw material diamine components for specific polyamides include aliphatic diamines such as tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,2,4-trimethyl-hexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine, as well as 1,3-bis(aminomethyl) Examples of alicyclic diamines such as cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, bis(4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis(aminomethyl)decalin, and bis(aminomethyl)tricyclodecane, as well as aromatic ring-containing diamines such as bis(4-aminophenyl) ether, paraphenylenediamine, and bis(aminomethyl)naphthalene, can be used individually or in combination of two or more.

[0019] Furthermore, the specific polyamide preferably contains α,ω-linear aliphatic dicarboxylic acid units having 4 to 20 carbon atoms as dicarboxylic acid units. Preferably, 75 mol% or more, more preferably 80 mol% or more, even more preferably 85 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and especially most preferably 99 mol% or more of the dicarboxylic acid units of the specific polyamide are derived from α,ω-linear aliphatic dicarboxylic acids having 4 to 20 carbon atoms.

[0020] As a C4-C20 α,ω-linear aliphatic dicarboxylic acid suitable for use as a raw material dicarboxylic acid component of a specific polyamide, C6-C16 α,ω-linear aliphatic dicarboxylic acids are preferred, and C8-C14 α,ω-linear aliphatic dicarboxylic acids are preferred. Specifically, C4-C20 α,ω-linear aliphatic dicarboxylic acids include adipic acid, sebacic acid, dodecanediic acid, tridecanediic acid, tetradecanediic acid, etc. Among these, sebacic acid is preferred because it brings the melting point of the specific polyamide into a range suitable for molding.

[0021] Examples of dicarboxylic acid components other than those mentioned above include phthalate compounds such as isophthalic acid, terephthalic acid, and orthophthalic acid, and isomers of naphthalenedicarboxylic acids such as 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid, which can be used individually or in mixtures of two or more.

[0022] It should be noted that while the specific polyamide is mainly composed of diamine units and dicarboxylic acid units, it does not mean that other constituent units are completely excluded, and it goes without saying that it may also contain constituent units derived from lactams such as ε-caprolactam and laurolactam, and aliphatic aminocarboxylic acids such as aminocaproic acid and aminoundecanoic acid. Here, "main components" refers to the fact that among the constituent units constituting the specific polyamide, the total number of diamine units and dicarboxylic acid-derived constituent units is the largest among all constituent units. In this embodiment, it is preferable that the total of diamine units and dicarboxylic acid units in the specific polyamide accounts for 90% by mass or more of the total constituent units, more preferably 95% by mass or more, even more preferably 97% by mass or more, and even more preferably 99% by mass or more.

[0023] For specific polyamides, it is also preferable to use polyamide resins manufactured using biomass raw materials (biomass polyamide resins). By using biomass polyamide resins, the environmental impact can be reduced. It is also possible to use raw material monomers that have been certified by Mass Balance Certification (ISCC PLUS). Mass balance certification means that the extent to which renewable raw materials and bio-raw materials are used in each factory or production facility, and how much of the product is produced or shipped, is quantified and guaranteed along with the quality.

[0024] The melting point of the specific polyamide is preferably 150°C or higher, more preferably 180°C or higher, even more preferably 200°C or higher, and preferably 350°C or lower, more preferably 330°C or lower, and even more preferably 300°C or lower.

[0025] The specific polyamide preferably has a lower limit of number-average molecular weight (Mn) of 6,000 or more, more preferably 8,000 or more, even more preferably 10,000 or more, and more preferably 100,000 or less, and more preferably 50,000 or less. Within this range, heat resistance, elastic modulus, dimensional stability, and moldability are improved.

[0026] The relative viscosity of the specified polyamide is preferably 1.9 or higher at the lower limit, more preferably 2.0 or higher, and even more preferably 2.1 or higher. On the other hand, the upper limit of the relative viscosity of the specified polyamide is preferably 4.0 or lower, more preferably 3.9 or lower, and even more preferably 3.8 or lower. The relative viscosity of the specified polyamide is measured under the conditions of JIS K 69020-2.

[0027] The semi-crystallization time of a specific polyamide at 160°C is not particularly limited, but is preferably 10 seconds or more, more preferably 15 seconds or more, even more preferably 20 seconds or more, and may be 30 seconds or more. The crystallization time is preferably 80 seconds or less, more preferably 50 seconds or less, even more preferably 40 seconds or less, and may be 35 seconds or less. When the foam contains two or more specific polyamides, it is preferable that the semi-crystallization time of the polyamide with the highest content is within the above range.

[0028] The content of the specific polyamide in the foam is preferably 40% by mass or more, more preferably 50% by mass or more, and may be 60% by mass or more depending on the application. Setting it above the lower limit tends to further improve fluidity during melting. The content of the specific polyamide in the foam is preferably 99% by mass or less, more preferably 95% by mass or less, and may be 90% by mass or less or 80% by mass or less depending on the application. The foam may contain only one type of specific polyamide or two or more types. When two or more types are included, it is preferable that the total amount is within the above range.

[0029] Furthermore, the foam of this embodiment may also preferably contain two or more specific polyamides. For example, by containing a first specific polyamide with a melting point of 260°C or less, or without a clear melting point, and a second specific polyamide with a melting point exceeding 260°C, the second specific polyamide can be used as a nucleating agent in the production of the foam. A nucleating agent is a material that serves as a starting point for the formation of crystal nuclei in a crystalline resin during molding, and can promote the generation and growth of crystal nuclei. As such a second specific polyamide, a specific polyamide in which the xylylenediamine in the xylylenediamine unit is para-xylylenediamine can be used. The preferred embodiment of the dicarboxylic acid unit in the second polyamide is as described above.

[0030] When the content of the first specific polyamide is 100 parts by mass, the content of the second specific polyamide is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 5 parts by mass or more, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and may also be 10 parts by mass or less.

[0031] <Other Polyamides> The foam of this embodiment may further contain other polyamides that do not fall under the category of specific polyamides. The type of other polyamide resin is not particularly defined and may be an aliphatic polyamide resin or a semi-aromatic polyamide resin. Examples of aliphatic polyamide resins include polyamide 4, polyamide 46, polyamide 6, polyamide 66, polyamide 666, polyamide 610, polyamide 11, polyamide 12, etc. Semi-aromatic polyamide resins are composed of diamine-derived structural units and dicarboxylic acid-derived structural units, and it is preferable that 20 to 80 mol% (preferably 30 to 80 mol%, more preferably 40 to 70 mol%) of the total structural units of the diamine-derived structural units and dicarboxylic acid-derived structural units contain aromatic rings. By using such a semi-aromatic polyamide resin, the mechanical strength of the resulting resin molded product can be increased. Examples of semi-aromatic polyamide resins include terephthalic acid-based polyamide resins (polyamide 6T, polyamide 6I / 6T, polyamide 9T, polyamide 10T), etc. In addition to the above, polyamide resins described in paragraphs 0012 to 0031 of Japanese Patent Publication No. 2022-139048 can also be used, and this information is incorporated herein.

[0032] The content of other polyamides in the foam is preferably 20% by mass or less, more preferably 10% by mass or less, and may be 5% by mass or less depending on the application. Furthermore, it may be 1% by mass or less, or 0.1% by mass or less. The foam may contain only one type of specific polyamide, or it may contain two or more types. When it contains two or more types, it is preferable that the total amount is within the above range.

[0033] <Inorganic Filler> The foam of this embodiment contains an inorganic filler. The inclusion of an inorganic filler may increase the mechanical strength, heat resistance, etc., of the foam. It is also possible to control the thermal conductivity characteristics of the foam. The type of inorganic filler is not particularly specified and may be any of the following: fibers, fillers, flakes, beads, etc., but fibers are preferred.

[0034] If the inorganic filler is a fiber, it may be a short fiber or a long fiber, with long fibers being preferred.

[0035] Examples of raw materials for inorganic fillers include inorganic substances such as glass, carbon (carbon fiber, etc.), alumina, boron, ceramics, metals (steel, etc.), asbestos, clay, zeolite, potassium titanate, barium sulfate, titanium dioxide, silicon dioxide, aluminum oxide, magnesium hydroxide, and plants (including kenaf, bamboo, etc.), with glass being preferred.

[0036] The foam of this embodiment preferably contains glass fibers as a reinforcing filler. The glass fibers are selected from glass compositions such as A glass, C glass, E glass, R glass, D glass, M glass, and S glass, with E glass (alkali-free glass) being particularly preferred. The number-average fiber diameter of the glass fibers is usually 1 to 25 μm, preferably 5 to 17 μm. By setting the number-average fiber diameter to 1 μm or more, the moldability of the foam tends to be further improved. By setting the number-average fiber diameter to 25 μm or less, the appearance of the resulting molded product tends to be improved, and the reinforcing effect also tends to be improved. The glass fibers may be single fibers or multiple single fibers twisted together. The form of the glass fibers may be chopped strands (for example, glass fibers cut to a length of 1 to 10 mm) or milled fibers (i.e., glass fibers crushed to a length of about 10 to 500 μm), but chopped strands are preferred. Glass fibers with different forms can also be used in combination. Furthermore, glass fibers are preferred to have a circular, polygonal, or irregularly shaped cross-section. The irregularly shaped cross-section is defined as having an oblateness ratio, which is the ratio of the major axis to the minor axis of the cross-section perpendicular to the length direction of the fiber, for example, 1.5 to 10, more preferably 2.5 to 10, even more preferably 2.5 to 8, and particularly preferably 2.5 to 5.

[0037] The glass fibers may be surface-treated with, for example, silane compounds, epoxy compounds, or urethane compounds, or oxidized, in order to improve their affinity with the resin components, as long as the properties of the foam of this embodiment are not significantly impaired.

[0038] The inorganic filler used in this embodiment may be a conductive filler. Specifically, examples include metals, metal oxides, and conductive carbon compounds, with conductive carbon compounds being preferred.

[0039] When the content of a specific polyamide is 100 parts by mass, the content of the inorganic filler (preferably glass fiber) is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and preferably 60% by mass or less, even more preferably 50% by mass or less, and may be 40% by mass or less. The content of the inorganic filler (preferably glass fiber) relative to the total mass of the foam is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, and may be 60 parts by mass or less. The foam of this embodiment may contain only one type of inorganic filler (preferably glass fiber) or may contain two or more types. When two or more types are included, it is preferable that the total amount is within the above range.

[0040] <Nucleating Agent> The foam of this embodiment may contain a nucleating agent. Including a nucleating agent can improve the appearance of the resulting molded article. The nucleating agent may be an organic or inorganic nucleating agent, but an inorganic nucleating agent is preferred. Examples include graphite, molybdenum disulfide, barium sulfate, talc, mica, calcium carbonate, sodium phosphate, boron nitride, and kaolin. It is preferable to include one or more selected from talc, mica, calcium carbonate, and boron nitride, more preferably one or more selected from talc and calcium carbonate, and even more preferably talc. The talc may be surface-treated with at least one compound selected from polyorganohydrogensiloxanes and organopolysiloxanes. In this case, the amount of siloxane compound attached to the talc is preferably 0.1 to 5% by mass of the talc.

[0041] The number average particle diameter of the nucleating agent preferably has a lower limit of 0.1 μm or more, more preferably 0.5 μm or more. The number average particle diameter of the nucleating agent preferably has an upper limit of 40 μm or less, more preferably 30 μm or less, still more preferably 28 μm or less, even more preferably 15 μm or less, and yet even more preferably 10 μm or less. By setting the number average particle diameter to 40 μm or less, the number of nucleating agents serving as nuclei increases compared to the blending amount of the nucleating agent, and thus the crystal structure tends to be more stabilized.

[0042] When the foam of the present embodiment contains a nucleating agent, the content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and still more preferably 3 parts by mass or more with respect to 100 parts by mass in total of the specific polyamide. Further, the upper limit of the content of the nucleating agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and still more preferably 10 parts by mass or less with respect to 100 parts by mass in total of the specific polyamide. The foam of the present embodiment may contain only one kind of nucleating agent or may contain two or more kinds. When two or more kinds are contained, the total amount preferably falls within the above range.

[0043] <Release Agent> The foam of this embodiment may contain a release agent. Examples of release agents include aliphatic carboxylic acids, salts of aliphatic carboxylic acids, esters of aliphatic carboxylic acids and alcohols, aliphatic hydrocarbon compounds with a number average molecular weight of 200 to 15,000, polysiloxane-based silicone oils, ketone waxes, and fatty acid amides. Aliphatic carboxylic acids, salts of aliphatic carboxylic acids, esters of aliphatic carboxylic acids and alcohols, and fatty acid amides are preferred, and salts of aliphatic carboxylic acids are more preferred. As salts of aliphatic carboxylic acids, metal salts are preferred, and sodium salts, potassium salts, lithium salts, aluminum salts, barium salts, zinc salts, or calcium salts are more preferred. Details of the release agent can be found in paragraphs 0055 to 0061 of Japanese Patent Application Publication No. 2018-095706, and these contents are incorporated herein by reference. If the foam of this embodiment contains a release agent, its content is preferably 0.05 to 3 parts by mass, more preferably 0.1 to 1 part by mass, and even more preferably 0.2 to 0.8 parts by mass, per 100 parts by mass of the specific polyamide. The foam of this embodiment may contain only one type of release agent or two or more types. If two or more types are included, it is preferable that the total amount is within the above range.

[0044] <Other Components> The foam of the present embodiment may further contain other components. It is preferable that the total of the specific polyamide, inorganic filler, foaming agent, nucleating agent, and mold release agent in the foam of the present embodiment occupies 90% by mass or more of the foam, more preferably 95% by mass or more, and still more preferably 99% by mass or more. Examples of other components include resin additives such as heat stabilizers, light stabilizers, antioxidants, ultraviolet ray inhibitors, alkalis, colorants, hydrolysis resistance improvers, matting agents, plasticizers, dispersants, antistatic agents, gelation inhibitors, and flame retardants. The resin additives preferably total 20.0% by mass or less, more preferably 10.0% by mass or less, still more preferably 5.0% by mass or less, and even more preferably 1.0% by mass or less based on the total mass of the foam. Only one kind of other additive may be used, or two or more kinds may be used in combination. Details of other additives can be referred to the descriptions in paragraphs 0130 to 0155 of Japanese Patent No. 4894982, and these contents are incorporated herein. Further, additives described in paragraphs 0047 to 0103 of International Publication No. 2021 / 241471 can be incorporated into the foam of the present embodiment without departing from the gist of the present invention, and this content is incorporated herein.

[0045] <Properties of the Foam> [Expansion Ratio] The expansion ratio of the foam of the present embodiment is preferably 1.3 to 3.0 times. The expansion ratio of the foam is preferably 1.4 times or more, more preferably 1.5 times or more. Also, the expansion ratio of the foam is preferably 2.9 times or less, more preferably 2.8 times or less.

[0046] [Specific Gravity] The specific gravity of the foam of the present embodiment is preferably 1.2 or less, more preferably 1.1 or less, and still more preferably 1.0 or less. The specific gravity of the foam is preferably 0.6 or more, more preferably 0.7 or more, and still more preferably 0.8 or more.

[0047] [Air Bubbles] The internal air bubbles of the foam of the present embodiment may be closed cells or open cells. The foam preferably has only closed cells or has both closed cells and open cells.

[0048] If the foam has closed cells, the size of the cells is 40 μm. ３ Preferably, it is 50 μm or more. ３ It is more preferable that the above is true. The upper limit of the bubble size is not particularly limited, but for example, 350 μm ３ Preferably, the following, 300 μm ３ The following is more preferable:

[0049] (Method for manufacturing foam) The method for manufacturing the foam of this embodiment is a method for manufacturing the foam of this embodiment as described above, and includes preparing a foaming material containing a polyamide containing xylylenediamine units, an inorganic filler, and a foaming agent (preparation step), and foaming the foaming material (foaming molding step).

[0050] <Preparation Step> The preparation step is a step of preparing a foaming material comprising a specific polyamide, an inorganic filler, and a blowing agent. The preparation step can be any known method for producing a blowing agent without particular limitation. Preferably, the preparation step includes mixing the specific polyamide, the inorganic filler, and the blowing agent. The foaming material may further contain the nucleating agent, release agent, and other components mentioned above. In this case, preferably, the preparation step includes mixing the specific polyamide, the inorganic filler, the blowing agent, and at least one of the nucleating agent, release agent, and other components mentioned above.

[0051] The components of these foaming materials may be mixed beforehand, with some components added before the remaining components are added, or all components may be mixed at once. For example, it is preferable to mix the resin and the foaming agent to form a masterbatch, and then mix this masterbatch with the inorganic filler. Furthermore, it is preferable that the inorganic filler (preferably glass fiber) is side-fed.

[0052] In the preparation process, the method of mixing the foaming materials is not particularly limited, and a wide range of known methods can be employed. Specifically, the foaming materials can be produced by pre-mixing each component using various mixers such as tumblers and Henschel mixers, and then melt-kneading them using, for example, a Banbury mixer, rolls, brabender, single-screw extruder, twin-screw extruder, or kneader.

[0053] The specific polyamides, inorganic fillers, nucleating agents, release agents, and other components in the foaming material are as described above.

[0054] [Foaming agents] Examples of foaming agents include chemical foaming agents and physical foaming agents.

[0055] Chemical blowing agents are blowing agents that generate gas and cause resins to foam when exposed to temperatures above their decomposition temperature. Specifically, examples include inorganic blowing agents such as sodium bicarbonate, nitroso compounds such as N,N'-dinitrosopentamethylenetetramine (DPT), azo compounds such as azodicarbonamide (ADCA) and barium azodicarboxylate (Ba / AC), organic blowing agents such as hydrazine compounds such as 4,4'-oxybis(benzenesulfonylhydrazide) (OBSH) and hydrradicalbondamide (HDCA), and tetrazole compounds. From a safety standpoint, inorganic blowing agents are preferred. These may be used individually or in combination of two or more.

[0056] The foaming agent content in the foaming material is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, relative to the total mass of the foaming material. Furthermore, the foaming agent content in the foaming material is preferably 1% by mass or less, more preferably 0.8% by mass or less, and even more preferably 0.5% by mass or less. Alternatively, a foaming agent masterbatch may be used, which is prepared by kneading a foaming agent and, if necessary, a known functional agent into a resin such as polyethylene, polypropylene, polystyrene, ethylene-vinyl acetate copolymer resin, or acrylonitrile-butadiene-styrene copolymer resin. When using a foaming agent masterbatch, it is preferable that the amount of foaming agent contained in the foaming agent masterbatch is within the above range relative to the total mass of the foaming material.

[0057] <Foam Molding Process> When manufacturing foam, known and conventional methods can be applied to the foam molding process. For example, foam can be obtained by extruding the foam material from a slit-shaped nozzle using an extruder to form a sheet, or by extruding the foam material from a round nozzle to form a strand. Furthermore, the shape of the foam may be formed by cutting the foam sheet or foam strand. It is also possible to thermoform the obtained extruded foam as is, or to cut it into foam particles and then mold them in a mold.

[0058] Alternatively, a method can be applied in which pellets of a specific polyamide are prepared in advance, the foaming agent is impregnated into the pellets under pressure, and then foamed by changes in temperature and pressure to produce foamed particles, which are then molded in a mold.

[0059] Furthermore, the foam molding process preferably includes filling the cavity of the mold with foaming material by injection. For example, by releasing the pressure inside the cavity after the filling, the foaming material can be foamed to obtain a foamed body.

[0060] For example, it is preferable to include increasing the cavity volume of the mold after filling the cavity of the mold with the foaming material by injection. For example, a foam can be obtained by an injection molding method called the core-back method, in which the foaming material is injected into a cavity formed in the mold of an injection molding machine, and immediately or after a predetermined time has elapsed, a movable mold, or a movable core installed inside the movable mold, is retracted to a predetermined position at a predetermined speed to expand the cavity space and cause foaming.

[0061] Furthermore, injection molding methods such as the short-shot method, in which a smaller amount of foaming material than the product portion is filled into the mold cavity when filling the resin, and the foam is expanded to form the product shape after foaming, or the full-shot method, in which an amount equal to the volume of the mold cavity is filled, and the solidification shrinkage is compensated for by the generation and expansion of bubbles, may be used. In addition, known embodiments may be adopted, such as lowering the temperature of the mold to a temperature lower than the temperature of the foaming material at the time of injection to suppress foaming on the surface of the foam that is in contact with the surface of the cavity, thereby providing a skin layer on the surface of the foam in which foaming has been suppressed.

[0062] Furthermore, the foam manufacturing method of this embodiment may include, without particular limitation, steps performed in the manufacturing of known foams.

[0063] <Shape and Use> There are no particular restrictions on the shape of the foam in this embodiment, and it can be appropriately selected according to the use and purpose of the molded product. Examples include plate-shaped, rod-shaped, sheet-shaped, film-shaped, cylindrical, annular, circular, elliptical, gear-shaped, polygonal, irregularly shaped, hollow, frame-shaped, box-shaped, and panel-shaped products.

[0064] The application fields of the foam of this embodiment are not specifically defined, but it can be widely used in automobile and other transport equipment parts, general machinery parts, precision machinery parts, electronic and electrical equipment parts, office automation equipment parts, building materials and housing equipment related parts, medical devices, leisure and sports goods, amusement equipment, medical supplies, daily necessities such as food packaging films, defense and aerospace products, etc.

[0065] In particular, the foam of this embodiment can be used in vehicles requiring lightweight materials, such as automobiles, aircraft, and ships. For example, in automotive applications, it can be used as interior components such as seats, ceilings, dashboards, panels, cushions, door trims, car seats, sound deadening, sun visors, and interior decorations; exterior components such as bumpers and car bodies; components of engines and other power mechanisms; vibration damping materials; sound absorbing materials; and heat insulating materials. By incorporating the foam of this embodiment into a vehicle, the weight of the vehicle can be reduced, and a reduction in energy consumption and carbon dioxide emissions to the environment can also be expected.

[0066] (Composition) The composition of this embodiment comprises a polyamide containing xylylenediamine units, an inorganic filler, and a foaming agent. The composition of this embodiment is preferably the foaming material described above. A preferred embodiment of the composition of this embodiment is the same as a preferred embodiment of the foaming material described above. The composition of this embodiment is suitably used as the foaming material described above.

[0067] The present invention will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing content, processing procedures, etc., shown in the following examples can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. If the measuring instruments, etc., used in the examples are difficult to obtain due to discontinuation or other reasons, measurements can be taken using other instruments with equivalent performance.

[0068] (Example) <Synthesis of MP10> Sebacic acid (manufactured by CASDA) was placed in a jacketed reaction vessel equipped with a stirrer, condenser, cooler, thermometer, dropping tank, and nitrogen gas inlet tube, and after thorough nitrogen purging, it was heated to 170°C and melted. While stirring the contents, a mixed amine of metaxylylenediamine and paraxylylenediamine (molar ratio: 70:30) (manufactured by Mitsubishi Gas Chemical Co., Ltd., MPXDA) was gradually added dropwise so that the molar ratio with sebacic acid was 1:1, and the temperature was raised to 240°C. After the dropwise addition was completed, the temperature was raised to 260°C and continued for 20 minutes. Thereafter, the internal pressure of the reaction system was continuously reduced to 0.08 MPa and the reaction was continued. After the reaction was completed, the reaction vessel was pressurized to 0.2 MPa with nitrogen gas, and the polymer was removed as strands from a nozzle at the bottom of the polymerization tank, cooled with water, and pelletized in a pelletizer to obtain the polymer. The melting point of the obtained MP10 was 215°C.

[0069] <Synthesis of MP6> In a jacketed reaction vessel equipped with a stirrer, condenser, condenser, thermometer, dropping tank, and nitrogen gas inlet tube, adipic acid (Roadia) was added and thoroughly purged with nitrogen. After heating to 170°C and melting, a mixed amine of metaxylylenediamine and paraxylylenediamine (molar ratio: 70:30) (Mitsubishi Gas Chemical Co., Ltd., MPXDA) was gradually added dropwise while stirring the contents, so that the molar ratio with adipic acid was 1:1, and the temperature was raised to 260°C. After the dropwise addition was complete, the temperature was raised to 280°C and continued for 20 minutes. Thereafter, the internal pressure of the reaction system was continuously reduced to 0.08 MPa and the reaction was continued. After the reaction was complete, the reaction vessel was pressurized with nitrogen gas to 0.2 MPa, and the polymer was removed as strands from a nozzle at the bottom of the polymerization tank. After water cooling, it was pelletized in a pelletizer to obtain the polymer. The melting point of the obtained MP6 was 258°C.

[0070] <Synthesis of MP12> Dodecanedioic acid was placed in a jacketed reaction vessel equipped with a stirrer, condenser, condenser, thermometer, dropping tank, and nitrogen gas inlet tube. After thorough nitrogen purging, it was heated to 180°C and melted. While stirring the contents, a mixed amine of metaxylylenediamine and paraxylylenediamine (molar ratio: 70:30) (manufactured by Mitsubishi Gas Chemical Co., Ltd., MPXDA) was gradually added dropwise to achieve a molar ratio of 1:1 with dodecanedioic acid, while the temperature was raised to 250°C. After the dropwise addition was completed, the reaction was continued for 20 minutes. Subsequently, the internal pressure of the reaction system was continuously reduced to 0.08 MPa, and the reaction was continued. After the reaction was complete, the reaction vessel was pressurized with nitrogen gas to 0.2 MPa, and the polymer was removed as strands from a nozzle at the bottom of the polymerization tank. After water cooling, it was pelletized in a pelletizer to obtain the polymer. The melting point of the obtained MP12 was 207°C.

[0071] <Synthesis of MXD6I> In a jacketed reaction vessel equipped with a stirrer, condenser, condenser, thermometer, dropping tank, and nitrogen gas inlet tube, a mixture of adipic acid and isophthalic acid (molar ratio: 94:6) was added, and after thorough nitrogen purging, it was heated to 180°C and melted. While stirring the contents, metaxylylenediamine was gradually added dropwise until the molar ratio of the adipic acid and isophthalic acid mixture was 1:1, and the temperature was raised to 265°C. After the dropwise addition was complete, the temperature was raised to 270°C and continued for 10 minutes. Thereafter, the internal pressure of the reaction system was continuously reduced to 0.08 MPa and the reaction was continued. After the reaction was complete, the reaction vessel was pressurized with nitrogen gas to 0.2 MPa, and the polymer was removed as strands from a nozzle at the bottom of the polymerization tank. After water cooling, the polymer was pelletized in a pelletizer to obtain the polymer. The melting point of the obtained MXD6I was 229°C.

[0072] <Synthesis of PXD10> Sebacic acid (manufactured by CASDA) was added to a jacketed reaction vessel equipped with a stirrer, condenser, condenser, thermometer, dropping tank, and nitrogen gas inlet tube. After thorough nitrogen purging, it was heated to 170°C and melted. While stirring the contents, paraxylylenediamine (manufactured by Showa Denko, PXDA) was gradually added dropwise to maintain a molar ratio of 1:1 with sebacic acid, and the temperature was raised to 290°C. After the dropwise addition was complete, the temperature was raised to 300°C and continued for 20 minutes. Subsequently, the internal pressure of the reaction system was continuously reduced to 0.08 MPa, and the reaction was continued for 20 minutes. After the reaction was complete, the reaction vessel was pressurized with nitrogen gas to 0.2 MPa, and the polymer was removed as strands from a nozzle at the bottom of the polymerization tank. After water cooling, it was pelletized in a pelletizer to obtain the polymer. The melting points of the obtained PXD10 were 280°C and 290°C.

[0073] <Foam Manufacturing> The foam was manufactured by pre-melting and kneading polyamide, inorganic filler, and release agent to obtain pellets, and then dry-blending a foaming agent to obtain a foam material. This foam material was then fed into the molding machine "MD-100X" and subjected to core-back molding. The cylinder temperature was 260°C, the mold temperature was 85°C, the filling time was 1.5 seconds, the holding pressure time was 1.3 seconds, the cooling time was 60 seconds, and the core-back amount was 1 mm (wall thickness before core-back was 2 mm).

[0074]

[0075] Details of each component listed in the table are as follows:

[0076] [Resin] ・MP10: The above synthetic product ・MP6: The above synthetic product ・MP12: The above synthetic product ・MXD6I: The above synthetic product ・PA6: UBE Nylon 1015GC6 (manufactured by Ube Industries, Ltd.) ・PXD10: The above synthetic product

[0077] [Inorganic filler] ・Glass fiber: T-275H (manufactured by Nippon Electric Glass Co., Ltd.)

[0078] [Foaming agent masterbatch] ・HB25A: Panslene HB25A (manufactured by Eiwa Kasei Kogyo Co., Ltd.) ・HB27A: Panslene HB27A (manufactured by Eiwa Kasei Kogyo Co., Ltd.) ・HB16A: Panslene HB16A (manufactured by Eiwa Kasei Kogyo Co., Ltd.)

[0079] [Nucleating agent] ・Talc: Micron White 5000S (manufactured by Hayashi Chemical Co., Ltd.)

[0080] [Release agent] ・CS-8CP: CS-8CP (manufactured by Nitto Chemical Industries, Ltd.)

[0081] <Evaluation> [Measurement of Semi-crystallization Time] For each foam material, resin pellets used in its manufacture were left to stand for 3 minutes in an air bath set to its melting point + 20°C. Then, the sample was placed between the light rays from the light source of an oil bath set to the measurement temperature, passing through a polarizing plate and reaching the sensor. The semi-crystallization time was calculated from the difference in voltage before and after crystallization. A shorter semi-crystallization time indicates a faster crystallization rate. The semi-crystallization measuring device used was the Kotaki Seisakusho MK-701. The measurement results are listed in the "Semi-crystallization Time" column of the table above. The unit of measurement in the table is seconds.

[0082] [Evaluation of Foaming State] The foaming state of the obtained foam was evaluated by microscopic observation of the foam cross-section, and the evaluation results were recorded in the "Foaming State" column of the table. The evaluation was carried out according to the following evaluation criteria. -Evaluation Criteria- A: Fine cells were introduced in a nearly uniform manner, and foaming was sufficient. B: Although coarse cells and small cracks could be observed, fine cells were generally introduced, and foaming occurred. C: Some coarse cells and cracks were noticeable. D: There were many coarse cells and cracks, and foaming was incomplete.

[0083] <Mechanical Properties of Foam> The mechanical properties of the structure were measured before and after foaming and are recorded in the table below.

[0084] Specific gravity: Calculated using an electronic hydrometer MDS-300 (manufactured by Alpha Mirage Co., Ltd.). Thickness (μm): Measured using a micrometer. Foaming ratio: Bending strength (MPa): Bending strength was measured by performing a bending test at a temperature of 23°C according to the method compliant with JIS K7171:2016. Bending strength retention rate (%): This is the bending strength after foaming, with the bending strength before foaming set to 100%. Bending modulus of elasticity (GPa): Bending modulus of elasticity was measured by performing a bending test at a temperature of 23°C according to the method compliant with JIS K7171:2016. Bending modulus of elasticity retention rate (%): This is the bending modulus of elasticity after foaming, with the bending modulus of elasticity before foaming set to 100%.

[0085]

[0086] <Measurement of Maximum Expansion Ratio> For each foaming material, the amount of foaming agent used was increased, and the foaming state was observed by microscopic observation of the cross-section of the foam. The maximum expansion ratio at which no cracks occurred in the cross-section was measured and recorded in the "Maximum Expansion Ratio" column of the table below.

[0087]

[0088] From the above results, it can be seen that the foam of this embodiment exhibits excellent retention of the flexural modulus before and after foaming. In the foam of Comparative Example 1, which uses a foaming material that does not contain a specific polyamide, the retention of the flexural modulus before and after foaming is low, and it can be seen that the flexural modulus after foaming is significantly lower than that before foaming. Furthermore, it can be seen that the foam of this embodiment is superior to Comparative Example 1, which uses a foaming material that does not contain a specific polyamide, in terms of foaming state, flexural strength after foaming, retention of flexural strength before and after foaming, flexural modulus after foaming, and maximum foaming ratio.

Claims

1. A foam containing a polyamide containing xylylenediamine units and an inorganic filler.

2. The foam according to claim 1, wherein the inorganic filler contains glass fibers.

3. The foam according to claim 1 or 2, wherein the xylylenediamine is metaxylylenediamine, paraxylylenediamine, or a mixture thereof.

4. The foam according to any one of claims 1 to 3, wherein the polyamide contains α,ω-linear aliphatic dicarboxylic acid units having 4 to 20 carbon atoms as dicarboxylic acid units.

5. The foam according to claim 4, wherein the α,ω-linear aliphatic dicarboxylic acid having 4 to 20 carbon atoms comprises sebaic acid.

6. The foam according to any one of claims 1 to 5, wherein the foaming ratio is 1.3 to 3.0 times.

7. The foam according to any one of claims 1 to 6, comprising two or more of the polyamides.

8. A method for producing a foam according to any one of claims 1 to 7, comprising: preparing a foaming material comprising a polyamide containing xylylenediamine units, an inorganic filler, and a foaming agent; and foaming the foaming material.

9. The method for producing a foam according to claim 8, wherein the foaming agent is a chemical foaming agent.

10. The method for producing a foam according to claim 8 or 9, wherein preparing the foaming material comprises mixing at least a polyamide containing xylylenediamine units, an inorganic filler, and a foaming agent.

11. The method for producing a foam according to any one of claims 8 to 10, wherein the foam molding includes filling the cavity of a mold with foam material by injection.

12. A method for producing a foam according to claim 11, comprising increasing the cavity volume of the mold after filling.

13. A composition comprising a polyamide containing xylylenediamine units, an inorganic filler, and a blowing agent.

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