JP7690697B2 - Resin composition, its manufacturing method, and molded article - Google Patents

Description

The present invention relates to a resin composition, a method for producing the same, and a molded article.

In order to build a sustainable society, composite resin compositions that combine petroleum-derived resin components with biomass components are increasingly being used. For example, Patent Document 1 proposes a composite resin composition that combines plant fibers such as regenerated cellulose fibers with polypropylene resin.

In such composite resin compositions, the inclusion of biomass components is expected to improve mechanical properties such as elastic modulus. However, little progress has been made in evaluating the performance changes and issues that arise when composite resin compositions are used over long periods of time.

JP 2011-21087 A

As a result of research by the present inventors, it was found that resin compositions containing regenerated cellulose fibers as a biomass component, in particular, have poor moist heat resistance. "Moist heat resistance" is one of the indicators for judging the deterioration of a resin composition during long-term use. After subjecting a resin composition (or a molded product) to moist heat treatment, the degree of deterioration of the resin composition during long-term use can be evaluated by comparing the mechanical properties such as tensile strength and flexural strength with those before treatment. As a result of research by the present inventors, it was found that under moist heat conditions, resin compositions containing regenerated cellulose fibers and polypropylene resin experience whitening and a decrease in strength due to the growth of voids at the interface between the regenerated cellulose fibers and the resin.

When polypropylene resin is compounded as a resin material, it is generally combined with an acid-modified polypropylene resin modified with maleic anhydride or the like. As a result of further investigation by the present inventors, it was found that the above-mentioned problems arise when this acid-modified polypropylene resin is combined with regenerated cellulose fiber. The acid-modified polypropylene resin is often added to improve the adhesion of the polypropylene resin to the fiber, and simply removing the acid-modified polypropylene resin makes it difficult to obtain the desired mechanical strength.

Therefore, the present invention aims to provide a resin composition that can provide molded articles having excellent moist heat resistance and good mechanical strength, a method for producing the same, and a molded article made from the resin composition.

The inventors of the present application further investigated the matter and concluded that the reason why the moist heat resistance of the composite resin composition as described above deteriorates is that when a molded article of a resin composition containing polypropylene resin, acid-modified polypropylene resin, and regenerated cellulose fibers is exposed to moist heat conditions, a reaction between the acid-modified polypropylene resin and cellulose progresses, accelerating the hydrolysis of the resin and cellulose fibers.

［２］前記樹脂組成物が、前記再生セルロース繊維（Ｂ）を長さ方向に揃えた繊維束に、前記ポリオレフィン樹脂（Ａ）と、前記エポキシ化合物（Ｃ）との混合物が含浸した、ポリオレフィン樹脂含浸再生セルロース繊維束（Ｂ１）を含む、［１］に記載の樹脂組成物。
［３］前記エポキシ化合物（Ｃ）が、エポキシ化油脂、エポキシ基含有共重合体、ビスフェノール型エポキシ化合物、及びエポキシシラン化合物からなる群より選択される少なくとも１つの化合物を含む、［１］または［２］に記載の樹脂組成物。
［４］前記ポリオレフィン樹脂（Ａ）の総質量に対する、前記酸変性ポリプロピレン樹脂（Ａ２）の割合が０．５～５質量％である、［１］から［３］のいずれかに記載の樹脂組成物。
［５］前記樹脂組成物の総質量に対する、前記ポリオレフィン樹脂（Ａ）の含有量が２５～９０質量％であり、前記再生セルロース繊維（Ｂ）の含有量が５～７０質量％であり、前記エポキシ化合物（Ｃ）の含有量が０．０５～５質量％である、［１］から［４］のいずれかに記載の樹脂組成物。
［６］前記酸変性ポリプロピレン樹脂（Ａ２）が、前記無水マレイン酸変性ポリプロピレン樹脂（ａ２）を含む、［１］から［５］のいずれかに記載の樹脂組成物。
［７］前記エポキシ化合物（Ｃ）が、エポキシ基含有共重合体、及びビスフェノール型エポキシ化合物からなる群より選択される少なくとも１つの化合物を含む、［１］から［６］のいずれかに記載の樹脂組成物。
［８］前記樹脂組成物中の、前記再生セルロース繊維（Ｂ）の平均繊維長が５～３０ｍｍである、［１］から［７］のいずれかに記載の樹脂組成物。
［９］［１］から［８］のいずれかに記載の樹脂組成物の成形品。
［１０］［１］から［８］のいずれかに記載の樹脂組成物の製造方法であって、
前記ポリオレフィン樹脂（Ａ）と、前記エポキシ化合物（Ｃ）との混合物を得ることと、前記混合物を前記再生セルロース繊維（Ｂ）に配合することとを含み、
前記混合物を得ることが、下記式（１）で表される、最終的に得られる前記樹脂組成物中の酸濃度に対するエポキシ基濃度の比（Ｒ）が０．９以上となるように、前記ポリオレフィン樹脂（Ａ）と前記エポキシ化合物（Ｃ）とを混合することを含む、樹脂組成物の製造方法。

As a result of intensive research, the inventors of the present application have surprisingly found that by combining an acid-modified polypropylene resin having an acid concentration (calculated as maleic anhydride) within a certain range with regenerated cellulose fiber, and further blending an epoxy compound having a specific epoxy group concentration to set the ratio of the epoxy group concentration to the acid concentration in the resin composition (epoxy group concentration/acid concentration) to 0.9 or more, the moist heat resistance of the resulting molded article is improved. Furthermore, the inventors have found that the molded article obtained from this resin composition also has good mechanical strength.
That is, the present invention has the following aspects.
[1] A resin composition comprising:
The resin composition comprises
A polyolefin resin (A) including a polypropylene resin (A1) and an acid-modified polypropylene resin (A2) which is at least one resin selected from a maleic acid-modified polypropylene resin (a1) and a maleic anhydride-modified polypropylene resin (a2) and has an acid concentration (in terms of maleic anhydride) (v1) of 0.01 to 0.5 moL/kg;
Regenerated cellulose fibers (B);
and an epoxy compound (C) having an epoxy group concentration (f1) of 0.1 to 6.0 mol/kg;
The content of the polyolefin resin (A) is 25 to 90 mass% and the content of the regenerated cellulose fiber (B) is 5 to 70 mass% relative to the total mass of the resin composition,
A resin composition, wherein the ratio (R) of an epoxy group concentration to an acid concentration in the resin composition, represented by the following formula (1), is 0.9 or more:

[2] The resin composition according to [1], comprising a polyolefin resin-impregnated regenerated cellulose fiber bundle (B1) in which the regenerated cellulose fiber (B) is aligned in the length direction and impregnated with a mixture of the polyolefin resin (A) and the epoxy compound (C).
[3] The resin composition according to [1] or [2], wherein the epoxy compound (C) includes at least one compound selected from the group consisting of epoxidized fats and oils, epoxy group-containing copolymers, bisphenol-type epoxy compounds, and epoxysilane compounds.
[4] The resin composition according to any one of [1] to [3], wherein the ratio of the acid-modified polypropylene resin (A2) to the total mass of the polyolefin resin (A) is 0.5 to 5 mass%.
[5] The resin composition according to any one of [1] to [4], wherein the content of the polyolefin resin (A) is 25 to 90 mass%, the content of the regenerated cellulose fiber (B) is 5 to 70 mass%, and the content of the epoxy compound (C) is 0.05 to 5 mass%, relative to the total mass of the resin composition.
[6] The resin composition according to any one of [1] to [5], wherein the acid-modified polypropylene resin (A2) contains the maleic anhydride-modified polypropylene resin (a2).
[7] The resin composition according to any one of [1] to [6], wherein the epoxy compound (C) includes at least one compound selected from the group consisting of an epoxy group-containing copolymer and a bisphenol type epoxy compound.
[8] The resin composition according to any one of [1] to [7], wherein the average fiber length of the regenerated cellulose fiber (B) in the resin composition is 5 to 30 mm.
[9] A molded article of the resin composition according to any one of [1] to [8].
[10] A method for producing a resin composition according to any one of [1] to [8],
The method includes obtaining a mixture of the polyolefin resin (A) and the epoxy compound (C), and blending the mixture with the regenerated cellulose fibers (B),
The method for producing a resin composition includes mixing the polyolefin resin (A) and the epoxy compound (C) so that the ratio (R) of an epoxy group concentration to an acid concentration in the finally obtained resin composition, which is represented by the following formula (1), is 0.9 or more.

According to the present invention, it is possible to provide a resin composition capable of producing molded articles having excellent moist heat resistance and good mechanical strength, a method for producing the same, and a molded article made from the resin composition.

One embodiment of the present invention is described in detail below, but the scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention. In addition, when multiple upper and lower limit values are described for a specific parameter, any upper and lower limit values can be combined to create a suitable numerical range. In addition, in this specification, the expression "X to Y" means "X or more and Y or less." For example, "10 to 50% by mass" means "10% by mass or more and 50% by mass or less."

本実施形態に係る樹脂組成物によれば、耐湿熱性に優れ、かつ機械強度も良好な成形品を提供できる。 [Resin composition]
The resin composition according to the present embodiment comprises a polyolefin resin (A) including a polypropylene resin (A1), a maleic acid-modified polypropylene resin (a1) and a maleic anhydride-modified polypropylene resin (a2), which is at least one resin selected from the group consisting of a maleic acid-modified polypropylene resin (a1) and a maleic anhydride-modified polypropylene resin (a2), and an acid-modified polypropylene resin (A2) having an acid concentration (equivalent to maleic anhydride) (v1) of 0.01 to 0.5 mol/kg, a regenerated cellulose fiber (B), and an epoxy compound (C) having an epoxy group concentration (f1) of 0.1 to 6.0 mol/kg, and the content of the polyolefin resin (A) relative to the total mass of the resin composition is 25 to 90 mass%, the content of the regenerated cellulose fiber (B) is 5 to 70 mass%, and the ratio (R) of the epoxy group concentration to the acid concentration in the resin composition, as represented by the following formula (1), is 0.9 or more.

According to the resin composition according to this embodiment, it is possible to provide a molded article having excellent moist heat resistance and good mechanical strength.

In the resin composition according to the present embodiment, the ratio (R) of the epoxy group concentration to the acid concentration in the resin composition, represented by the above formula (1) (hereinafter simply referred to as "ratio (R)"), is 0.9 or more. In one embodiment, the ratio (R) is preferably 1.0 or more, more preferably 1.5 or more, and even more preferably 2.0 or more. The upper limit of the ratio (R) is not particularly limited, but from the viewpoint of the dispersibility of the epoxy compound (C) in the resin composition, it may be 5.0 or less, or 4.0 or less. In a preferred embodiment, the ratio (R) may be 0.9 to 5.0, 1.0 to 5.0, 1.5 to 4.0, or 1.6 to 3.1. As shown in formula (1), the acid concentration in the resin composition (the value corresponding to the denominator of formula (1)) can be calculated by multiplying the mass (kg/kg) of the acid-modified polypropylene resin (A2) in 1 kg of the resin composition by the acid concentration (v1) (moL/kg). Similarly, the epoxy group concentration in the resin composition (a value corresponding to the numerator of formula (1)) can be calculated by multiplying the mass (kg/kg) of the epoxy compound (C) in 1 kg of the resin composition by the epoxy group concentration (f1) (moL/kg).

<Polyolefin resin (A)>
The resin composition according to the present embodiment may contain a polyolefin resin (A) containing a polypropylene resin (A1) and an acid-modified polypropylene resin (A2). The content of the polyolefin resin (A) is 25 to 90 mass% based on the total mass of the resin composition. The content of the polyolefin resin (A) (hereinafter, sometimes referred to as "resin (A)") in the resin composition is within the range of 25 to 90 mass%, and can be arbitrarily adjusted within the range in which the ratio (R) is 0.9 or more.

(Polypropylene resin (A1))
Resin (A) according to the present embodiment includes polypropylene resin (A1). Examples of polypropylene resin (A1) (hereinafter, sometimes referred to as "resin (A1)") include propylene homopolymer (hereinafter, sometimes referred to as "PP homopolymer") and copolymer of propylene and an α-olefin other than propylene. Note that resin (A1) does not include polypropylene resin modified with maleic acid or maleic anhydride, which will be described later.

Examples of the propylene homopolymer include isotactic polypropylene and syndiotactic polypropylene. These may be used alone or in combination of two or more.
Examples of α-olefins other than propylene include ethylene, butene, hexene, and heptene. These may be used alone or in combination of two or more. Among these, preferred copolymers of propylene and α-olefins other than propylene include block copolymers of propylene and ethylene and random copolymers of propylene and ethylene.
In one embodiment, the resin (A1) preferably includes at least one resin selected from the group consisting of a PP homopolymer, a block copolymer of propylene and ethylene (hereinafter sometimes referred to as a “PP block copolymer”), and a random copolymer of propylene and ethylene, and more preferably includes at least one resin selected from the group consisting of a PP homopolymer and a PP block copolymer.

In one embodiment, the resin (A1) may be a polypropylene resin having a melt flow rate (MFR) (230°C, 2.16 kg load) of 20 to 300 g/10 min measured in accordance with ISO 1133.

In one embodiment, the proportion of resin (A1) in resin (A) may be in the range of 90 to 99.95% by mass, 93 to 99.95% by mass, 95 to 99.95% by mass, 97 to 99.95% by mass, or 99 to 99.92% by mass, based on the total mass of resin (A). In one embodiment, the proportion of resin (A1) in resin (A) may be 97 to 98.5% by mass. If the proportion of resin (A1) in resin (A) is within the above range, it becomes easier to adjust the acid concentration in the resin composition, and the resin composition is likely to have a ratio (R) of 0.9 or more.

In one embodiment, the proportion of resin (A1) in the resin composition may be 22.5 to 89.5 mass%, 35 to 89.5 mass%, 50 to 89.5 mass%, 60 to 89.5 mass%, or 65 to 70 mass%, relative to the total mass of the resin composition.

(Acid-modified polypropylene resin (A2))
The resin (A) according to the present embodiment is at least one resin selected from maleic acid-modified polypropylene resins (a1) and maleic anhydride-modified polypropylene resins (a2), and includes an acid-modified polypropylene resin (A2) having an acid concentration (equivalent to maleic anhydride) (v1) of 0.01 to 0.5 moL/kg.
By combining an acid-modified polypropylene resin (A2) (hereinafter sometimes referred to as "resin (A2)") having an acid concentration (v1) in the range of 0.01 to 0.5 mol/kg with an epoxy compound (C) described below and adjusting the ratio (R) in the resin composition to 0.9 or more, a molded product having excellent moist heat resistance and good mechanical strength can be obtained. Note that the "acid concentration (v1)" is the value of the raw material resin (A2), and the manufacturer's nominal value can be used.

In one embodiment, from the viewpoint of easily adjusting the ratio (R) in the resin composition to 0.9 or more, the acid concentration (v1) of the resin (A2) may be 0.01 to 0.21 mol/kg, 0.01 to 0.11 mol/kg, or 0.10 to 0.21 mol/kg. Alternatively, the acid concentration (v1) may be 0.11 to 0.5 mol/kg, or 0.2 to 0.5 mol/kg. The acid concentration (v1) of the resin (A2) can be controlled by adjusting the degree of modification (acid value) of maleic acid and/or maleic anhydride in the maleic acid-modified polypropylene resin (a1) and/or maleic anhydride-modified polypropylene resin (a2) described below.

(Maleic acid modified polypropylene resin (a1), maleic anhydride modified polypropylene resin (a2))
The resin (A2) according to this embodiment is at least one resin selected from maleic acid-modified polypropylene resin (a1) (hereinafter, also referred to as "resin (a1)") and maleic anhydride-modified polypropylene resin (a2) (hereinafter, also referred to as "resin (a2)").
In a preferred embodiment, the resin (a1) and the resin (a2) may be an acid-modified polypropylene resin obtained by graft polymerization of maleic acid or maleic anhydride to polypropylene. The polypropylene in the resins (a1) and (a2) may be a PP homopolymer or a PP block copolymer.

In one embodiment, resin (a1) and resin (a2) may be commercially available products. Examples of commercially available products include "MODIC (registered trademark) P908" (acid concentration (v1): 0.11 mol/kg) manufactured by Mitsubishi Chemical Corporation, "OREVAC (registered trademark) CA100" (acid concentration (v1): 0.11 mol/kg) manufactured by SK Functional Polymers, and "POLYBOND (registered trademark) 3200" (acid concentration (v1): 0.21 mol/g) manufactured by SI Group. These resins (a1) and (a2) may be used alone or in combination of two or more types.

In one embodiment, the resin (A2) may have an acid concentration (v1) of 0.01 to 0.5 mol/kg and an MFR (190°C, 2.16 kg load) of 50 g/10 min or more. If the MFR (190°C, 2.16 kg load) is 50 g/10 min or more, the dispersibility of the resin is easily improved, which is preferable.

In one embodiment, the ratio of resin (A2) in resin (A) may be 0.05 to 10% by mass, 0.05 to 7% by mass, 0.05 to 5% by mass, 0.05 to 3% by mass, or 0.08 to 1% by mass, based on the total mass of resin (A). In one embodiment, the ratio of resin (A2) in resin (A) may be 1.5 to 3% by mass, based on the total mass of resin (A). If the ratio of resin (A2) in resin (A) is within the above range, it becomes easier to adjust the acid concentration in the resin composition, and it is easy to obtain a resin composition with a ratio (R) of 0.9 or more. In addition, when resin (A2) contains resin (a2), the ratio of resin (a2) in resin (A) may be in the same range as the ratio of resin (A2) described above. That is, the proportion of resin (a2) in resin (A) may be 0.05 to 10 mass%, 0.05 to 7 mass%, 0.05 to 5 mass%, 0.05 to 3 mass%, 0.08 to 1 mass%, or 1.5 to 3 mass%, relative to the total mass of resin (A).

In one embodiment, from the viewpoint of easily adjusting the ratio (R) to 0.9 or more, the acid concentration in the resin composition may be 0.05 to 3.0 mmoL/kg, 0.05 to 2.6 mmoL/kg, 0.05 to 1.0 mmoL/kg, or 0.05 to 0.5 mmoL/kg. The acid concentration may also be 1.1 to 2.4 mmoL/kg.

(Other polyolefin resins)
In one embodiment, the resin (A) may contain a resin (another polyolefin resin) other than the above-mentioned resin (A1) and resin (A2).
The other polyolefin resins are not particularly limited as long as they have the effects of the present invention, and examples thereof include homopolymers or copolymers of olefins having 2 to 6 carbon atoms other than resin (A1) and resin (A2) (ethylene-based resins such as polyethylene and ethylene-propylene copolymers; poly(methylpentene-1); propylene-methylpentene copolymers, etc.); copolymers of olefins having 2 to 6 carbon atoms and copolymerizable monomers (ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester copolymers, etc.); homopolymers or copolymers of cyclic olefins (particularly cyclic olefins condensed with a hydrocarbon ring, bridged cyclic olefins, etc.) which may have a substituent such as an alkyl group or an ester group (for example, homopolymers of cyclic olefins such as polybicyclopentadiene and polynorbornene; copolymers of cyclic olefins selected from bicycloalkadienes, tricycloalkadienes, bicycloalkenes, and tricycloalkenes and α-olefins having 2 to 4 carbon atoms (ethylene, etc.)). These may be used alone or in combination of two or more types.
When resin (A) contains other polyolefin resins, the amount of the other polyolefin resins can be adjusted as desired so that the ratio (R) of the final resin composition is 0.9 or more, and it is preferable that the amount of the other polyolefin resins is 50 mass% or less relative to the total mass of resin (A).
In addition, the resin (A) may contain, as an optional component, a thermoplastic resin other than the above-mentioned resin (A1), resin (A2), and other polyolefin resins, so long as the ratio (R) of the final resin composition is 0.9 or more. However, it is preferable that the amount of the thermoplastic resin is 20 mass% or less relative to the total mass of the resin (A).

<Regenerated Cellulose Fiber (B)>
The resin composition according to the present embodiment includes regenerated cellulose fiber (B). The content of the regenerated cellulose fiber (B) in the resin composition is 5 to 70% by mass, based on the total mass of the resin composition. From the viewpoint of manufacturability of pellets and molded products, the content of the regenerated cellulose fiber (B) in the resin composition may be 10 to 60% by mass, 10 to 50% by mass, or 10 to 40% by mass, based on the total mass of the resin composition. In one embodiment, the content of the regenerated cellulose fiber (B) in the resin composition may be 40 to 70% by mass, 50 to 70% by mass, or 60 to 70% by mass, based on the total mass of the resin composition.

In this specification, "regenerated cellulose fibers" refers to natural cellulose fibers (cellulose fibers derived from higher plants, cellulose fibers derived from animals, and cellulose fibers derived from bacteria) and/or cellulose fibers artificially spun using chemically synthesized cellulose fibers.

Examples of cellulose fibers derived from higher plants include natural cellulose fibers (pulp fibers) such as wood fibers (wood pulp of conifers, broad-leaved trees, etc.), bamboo fibers, sugarcane fibers, seed hair fibers (cotton linters, bombax cotton, kapok, etc.), ginseng bark fibers (e.g., hemp, paper mulberry, mitsumata, etc.), and leaf fibers (e.g., Manila hemp, New Zealand hemp, etc.).
Examples of cellulose fibers derived from animals include sea squirt cellulose.

Examples of chemically synthesized cellulose fibers include organic acid esters such as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate; inorganic acid esters such as cellulose nitrate, cellulose sulfate, and cellulose phosphate; mixed acid esters such as cellulose acetate nitrate; hydroxyalkyl celluloses (e.g., hydroxyethyl cellulose (HEC), hydroxypropyl cellulose, etc.); carboxyalkyl celluloses (carboxymethyl cellulose (CMC), carboxyethyl cellulose, etc.); alkyl celluloses (methyl cellulose, ethyl cellulose, etc.); and cellulose derivatives such as regenerated celluloses (rayon, cellophane, etc.).
These natural cellulose fibers and chemically synthesized cellulose fibers may be used alone or in combination of two or more kinds.

Methods for obtaining regenerated cellulose fibers from the above-mentioned cellulose fibers include, for example, the viscose method, the cuprammonium method, and the solvent spinning method (a direct method that does not chemically convert cellulose once). Examples of regenerated cellulose fibers obtained by the viscose method include viscose rayon, polynosic, and modal. Examples of regenerated cellulose fibers obtained by the cuprammonium method include cupra. Examples of regenerated cellulose fibers obtained by the solvent spinning method include lyocell and tencel. As the regenerated cellulose fiber (B), one of these regenerated cellulose fibers may be used alone, or two or more of them may be used in combination.
In one embodiment, the regenerated cellulose fiber (B) preferably contains regenerated cellulose fiber obtained by the viscose method, and more preferably contains viscose rayon. When the regenerated cellulose fiber (B) contains regenerated cellulose fiber obtained by the viscose method, the mechanical strength of the obtained molded product tends to be good.

In one embodiment, the average fiber diameter of the regenerated cellulose fiber (B) is preferably 5 to 30 μm, and the degree of X-ray orientation is preferably 86% or more. By having such an average fiber diameter and degree of X-ray orientation, the regenerated cellulose fiber (B) is easily impregnated with the resin (A). In addition, the mechanical strength of the obtained molded product is also easily improved.
The average fiber diameter is more preferably 6 to 20 μm, and even more preferably 7 to 15 μm. The average fiber diameter of the regenerated cellulose fiber (B) can be calculated from the average diameter (major axis) of a plurality of fibers observed by SEM or the like.
The degree of X-ray orientation is more preferably 90% or more. The degree of X-ray orientation of the regenerated cellulose fibers (B) can be calculated from the formulas described in JP-A-9-31744 and JP-A-9-256216.

In one embodiment, the tensile modulus (Young's modulus) of the regenerated cellulose fiber (B) may be 10 GPa or more, 13 GPa or more, or 15 GPa or more. The tensile modulus of the regenerated cellulose fiber (B) can be determined by the method described in paragraph 0038 of JP 2013-91775 A, in which "after storage for three weeks in an air-conditioned room at 23°C and 50% RH, measurement was performed at a chuck distance of 200 mm and a pulling speed of 200 mm/min."

In one embodiment, it is preferable to use long fibers as the regenerated cellulose fibers (B). When long fibers are used as the regenerated cellulose fibers (B), the average fiber length of the regenerated cellulose fibers (B) in the resin composition is preferably 5 to 30 mm, more preferably 5 to 15 mm, and even more preferably 5 to 10 mm. By including such regenerated cellulose fibers (B), the mechanical strength of the molded product obtained by injection molding this is more likely to be improved.

In one embodiment, the resin composition may include a polyolefin resin-impregnated regenerated cellulose fiber bundle (B1) in which a fiber bundle in which regenerated cellulose fibers (B) are aligned in the length direction and bundled is impregnated with resin (A). That is, the resin composition according to this embodiment may be configured to include a polyolefin resin-impregnated regenerated cellulose fiber bundle (B1) containing resin (A) and regenerated cellulose fiber (B), and an epoxy compound (C) described below. In a preferred embodiment, the polyolefin resin-impregnated regenerated cellulose fiber bundle (B1) may be obtained by impregnating regenerated cellulose fiber (B) with a mixture containing resin (A) and epoxy compound (C). The details of the polyolefin resin-impregnated regenerated cellulose fiber bundle (B1) are described below.

(Polyolefin resin-impregnated regenerated cellulose fiber bundle (B1))
The polyolefin resin-impregnated regenerated cellulose fiber bundle (B1) (hereinafter sometimes simply referred to as "fiber bundle (B1)") is a composite material obtained by impregnating a fiber bundle of regenerated cellulose fibers (B) aligned in the length direction with a resin (A) and then cutting the fiber bundle. In a preferred embodiment, the fiber bundle may be a composite material obtained by impregnating the fiber bundle with a mixture of an epoxy compound (C) described below and the resin (A) and then cutting the fiber bundle. In this embodiment, the fiber bundle (B1) includes those impregnated with the resin (A) and those impregnated with a mixture of the resin (A) and the epoxy compound (C) (hereinafter sometimes simply referred to as "mixture").
In one embodiment, the average fiber length of the regenerated cellulose fibers (B) in the fiber bundle (B1) may be 5 to 30 mm, 5 to 15 mm, or 5 to 10 mm. The fiber length of the regenerated cellulose fibers (B) in the fiber bundle (B1) is the same as the length of the major axis of the fiber bundle (B1). Therefore, the average fiber length can be calculated from the average value of the major axis lengths of about 100 pellet-shaped fiber bundles (B1) measured with a caliper or the like.

The number of regenerated cellulose fibers (B) in the fiber bundle (B1) is preferably 2,000 to 30,000, more preferably 3,000 to 25,000, and even more preferably 5,000 to 25,000. If the number of regenerated cellulose fibers (B) is within the above range, the resin (A) (or mixture) can be easily impregnated up to the center of the fiber bundle (B1). As a result, when a resin composition containing the fiber bundle (B1) is molded, a molded product with a better appearance and superior mechanical strength can be easily obtained. In addition, manufacturing problems such as breakage of the fiber bundle are unlikely to occur during the production of the fiber bundle (B1).

In one embodiment, the fiber bundle (B1) can be produced by a known production method using a die. Specifically, the production methods described in JP-A-6-313050, JP-A-2007-176227, JP-B-6-2344, etc. can be applied.

In one embodiment, when the fiber bundle (B1) is composed of the resin (A) and the regenerated cellulose fiber (B), the ratio of the regenerated cellulose fiber (B) to the total mass of the fiber bundle (B1) is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, even more preferably 10 to 50% by mass, and particularly preferably 10 to 40% by mass. The ratio of the resin (A) in the fiber bundle (B1) is preferably 30 to 95% by mass, more preferably 50 to 90% by mass, even more preferably 60 to 90% by mass, and particularly preferably 60 to 80% by mass. By adjusting the ratio of the regenerated cellulose fiber (B) to the total mass of the fiber bundle (B1) within the above range, the fluidity during injection molding and the mechanical strength of the molded product tend to be better. In addition, even when the fiber bundle (B1) is composed of the mixture and the regenerated cellulose fiber (B), the ratio of the regenerated cellulose fiber (B) in the fiber bundle (B1) can be arbitrarily adjusted within the above range. The same applies to the ratio of the resin (A).

In one embodiment, the fiber bundle (B1) may contain known flame retardants and flame retardant assistants, heat stabilizers, lubricants, light stabilizers, antioxidants, colorants, release agents, antistatic agents, etc., within the range that does not impair the effects of the present invention.

<Epoxy Compound (C)>
The resin composition according to this embodiment contains an epoxy compound (C) having an epoxy group concentration (f1) of 0.1 to 6.0 mol/kg. By combining such an epoxy compound (C) with a resin (A) and regenerated cellulose fibers (B) and adjusting the ratio (R) in the resin composition to 0.9 or more, a molded article having excellent moisture and heat resistance can be obtained. The obtained molded article also has good mechanical strength. The "epoxy group concentration (f1)" is the value of the epoxy compound (C) in the raw material, and the manufacturer's nominal value can be adopted.

In one embodiment, from the viewpoint that the ratio (R) in the resin composition is likely to be 0.9 or more, the epoxy group concentration (f1) may be 0.1 to 5.0 mol/kg, 0.1 to 4.5 mol/kg, or 0.2 to 4.2 mol/kg. Alternatively, the epoxy group concentration (f1) may be 1.0 to 6.0 mol/kg, 1.7 to 6.0 mol/kg, or 1.7 to 5.2 mol/kg.

The epoxy compound (C) is not particularly limited as long as the epoxy group concentration (f1) is within the above-mentioned range, and conventionally known epoxy compounds can be used. Among these, from the viewpoint of cost and ease of handling, the epoxy compound (C) preferably contains at least one compound selected from the group consisting of epoxidized oils and fats, epoxy group-containing copolymers, bisphenol-type epoxy compounds, and epoxysilane compounds, each having an epoxy group concentration (f1) of 0.1 to 6.0 mol/kg, and more preferably contains at least one compound selected from the group consisting of epoxy group-containing copolymers and bisphenol-type epoxy compounds.

As the epoxidized fats and oils, for example, epoxidized triglycerides and epoxidized fatty acid monoesters can be used. As the epoxidized triglycerides, for example, epoxidized soybean oil, epoxidized linseed oil, etc. can be mentioned. In addition, the alkyl group (R ₂ ) of the alkyl ester portion in the epoxidized fatty acid monoester (R ₁ COOR ₂ ) can be, for example, a linear or branched alkyl group having 4 to 12 carbon atoms. More specifically, epoxidized fatty acid butyl, epoxidized fatty acid octyl, etc. can be mentioned. These epoxidized fats and oils may be used alone or in combination of two or more kinds. Among them, from the viewpoint of cost and handling, it is preferable to use epoxidized soybean oil. In addition, as the epoxidized fats and oils having an epoxy group concentration (f1) of 0.1 to 6.0 mol/kg, commercially available products may be used. An example of a commercially available product is "Adekacizer (registered trademark) O-130P" (epoxy group concentration (f1): 4.2 moL/kg) manufactured by ADEKA CORPORATION.

The epoxy group-containing copolymer may be, for example, at least one selected from the group consisting of an epoxy group-containing olefin-based polymer (hereinafter, sometimes referred to as "polymer (I)") and an epoxy group-containing styrene-based polymer (hereinafter, sometimes referred to as "polymer (II)").
An example of the polymer (I) is a copolymer composed of a repeating unit derived from an α-olefin and a repeating unit derived from a glycidyl ester of an α,β-unsaturated acid.

The α-olefin is not particularly limited, and examples thereof include ethylene, propylene, butene, and among these, ethylene is preferably used.
The glycidyl ester of an α,β-unsaturated acid is a compound represented by the following general formula (2). In the following general formula (2), R' represents hydrogen, a lower alkyl group having 1 to 5 carbon atoms and having a straight or branched chain, or a -R ₃ -COOH group (R ₃ represents an alkylene group having 1 to 5 carbon atoms and having a straight or branched chain). Of these, the glycidyl ester of an α,β-unsaturated acid is preferably acrylic acid glycidyl ester, methacrylic acid glycidyl ester, ethacrylic acid glycidyl ester, or itaconic acid glycidyl ester. From the viewpoints of cost and ease of handling, it is particularly preferable that the glycidyl ester of α,β-unsaturated acid includes methacrylic acid glycidyl ester.

In one embodiment, polymer (I) may contain, in addition to the above two components, a repeating unit derived from one or more olefin-based unsaturated esters such as acrylonitrile, acrylic acid esters, methacrylic acid esters, and α-methylstyrene as a third component, within a range that does not impair the effects of the present invention. When the third component is contained, any amount of the third component may be blended within a range in which the epoxy group concentration (f1) of polymer (I) is 0.1 to 6.0 moL/kg.

Polymer (I) can be prepared by a conventional radical polymerization method using monomers corresponding to the aforementioned components and a radical polymerization catalyst. Specifically, it can be produced by copolymerizing an α-olefin and a glycidyl ester of an α,β-unsaturated acid in the presence of a radical polymerization catalyst at 500 to 4000 atm and 100 to 300°C. The polymerization may be carried out in the presence or absence of a solvent or a chain transfer agent. Alternatively, it can be produced by mixing an α-olefin, a glycidyl ester of an α,β-unsaturated acid, and a radical polymerization catalyst, and melt-graft-copolymerizing the mixture in an extruder.

An example of polymer (II) is a copolymer composed of repeating units derived from styrenes and repeating units derived from a glycidyl ester of an α,β-unsaturated acid. Examples of the glycidyl ester of an α,β-unsaturated acid include the same as those for polymer (I), and preferred examples are also the same.

Examples of styrenes include styrene, α-methylstyrene, halogenated styrenes (e.g., brominated styrene), and divinylbenzene. Of these, styrene is preferably used.

In one embodiment, polymer (II) may be a multicomponent copolymer containing, in addition to the above two components, a repeating unit derived from one or more other vinyl monomers as a third component, within a range that does not impair the effects of the present invention. A suitable third component is a repeating unit derived from one or more olefin-based unsaturated esters such as acrylonitrile, acrylic acid esters, and methacrylic acid esters. When the third component is included, any amount can be blended within a range in which the epoxy group concentration (f1) of polymer (II) is 0.1 to 6.0 mol/kg.

Polymer (II) can be prepared by a conventional radical polymerization method using monomers corresponding to the aforementioned components and a radical polymerization catalyst. Specifically, it can be produced by copolymerizing styrenes and glycidyl esters of α,β-unsaturated acids in the presence of a radical polymerization catalyst at 500 to 4000 atm and 100 to 300°C. The polymerization may be carried out in the presence or absence of a solvent or a chain transfer agent. Alternatively, it can be produced by mixing an α-olefin with a glycidyl ester of α,β-unsaturated acid and a radical polymerization catalyst, and melt-graft-copolymerizing the mixture in an extruder.

In one embodiment, from the viewpoint of the heat resistance of the obtained molded article being more favorable and the moist heat resistance being easily improved, it is preferable to contain the polymer (I), more preferable to contain the polymer (I) containing an acrylic acid ester as the third component, and particularly preferable to contain ethylene-glycidyl methacrylate-methyl acrylate.
When polymer (I) and polymer (II) are used in combination, the ratio of these polymers can be appropriately adjusted according to the required properties.

Preferred examples of bisphenol-type epoxy compounds include bisphenol A-type epoxy compounds, bisphenol F-type epoxy compounds, and bisphenol AD-type epoxy compounds. Among them, from the viewpoint of cost and ease of handling, bisphenol A-type epoxy compounds and bisphenol F-type epoxy compounds are more preferred, and bisphenol A-type epoxy compounds are particularly preferred. The bisphenol-type epoxy compounds may be used alone or in combination of two or more types.

Examples of epoxy silane compounds include 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl methyl dimethoxysilane, β-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, etc. The epoxy silane compounds may be used alone or in combination of two or more.

In one embodiment, it is particularly preferred that the epoxy compound (C) comprises at least one compound selected from epoxidized soybean oil, ethylene-glycidyl methacrylate-methyl acrylate, and bisphenol A type epoxy compounds having an epoxy group concentration (f1) of 0.1 to 6.0 moL/kg.

In one embodiment, from the viewpoint of easily adjusting the ratio (R) to 0.9 or more, the proportion of the epoxy compound (C) contained in the resin composition is preferably 0.05 to 5 mass%, more preferably 0.05 to 4 mass%, even more preferably 0.05 to 3 mass%, and particularly preferably 0.08 to 2 mass%, relative to the total mass of the resin composition. In addition, the epoxy group concentration in the resin composition is preferably 2.0 to 6.8 mmoL/kg, more preferably 2.0 to 5.5 mmoL/kg, and even more preferably 2.1 to 5.0 mmoL/kg.

<Other ingredients>
The resin composition according to the present embodiment may contain components (other components) other than the resin (A), regenerated cellulose fiber (B) and epoxy compound (C) within a range that does not inhibit the effects of the present invention. Examples of other components include softeners, surface lubricants, leveling agents, antioxidants, surfactants, corrosion inhibitors, light stabilizers, ultraviolet absorbers, heat stabilizers, polymerization inhibitors, silane coupling agents (excluding epoxy silane compounds), lubricants, plasticizers, crystallization accelerators, hydrolysis inhibitors, inorganic fillers, organic fillers other than those derived from plants, metal powders, pigments, etc. These may be used alone or in combination of two or more. When the resin composition contains other components, the amount of the other components may be 1% by mass or less relative to the total mass of the resin composition.

<Method of producing resin composition>
The resin composition according to this embodiment includes obtaining a mixture of a polyolefin resin (A) and the aforementioned epoxy compound (C) and blending the mixture with regenerated cellulose fiber (B), and can be produced by a method in which the obtaining of the mixture includes mixing the polyolefin resin (A) and the epoxy compound (C) so that the ratio (R) of the epoxy group concentration to the acid concentration in the final resin composition, as represented by the following formula (1), is 0.9 or more.

A method of mixing the polyolefin resin (A) with the epoxy compound (C) described above includes first calculating the acid concentration in the polyolefin resin (A), then mixing the polyolefin resin (A), the epoxy compound (C) and optional components as necessary so that the ratio (R) in the final resin composition is 0.9 or more, and feeding the mixture into a twin-screw extruder, and then melt-kneading the mixture at a temperature of 160 to 280°C, more preferably 180 to 260°C, to obtain a mixture. The resin composition according to this embodiment may then be obtained by impregnating a molten mixture containing the polyolefin resin (A), the epoxy compound (C) and optional components as necessary into a fiber bundle of regenerated cellulose fibers (B) aligned in the length direction that have been passed through a crosshead die.

[Molded product and its manufacturing method]
The molded article according to the present embodiment is obtained by molding the above-mentioned resin composition. The molded article according to the present embodiment may be obtained by injection molding the above-mentioned resin composition. Since the molded article according to the present embodiment is obtained by molding the above-mentioned resin composition, it has excellent moist heat resistance and good mechanical strength.

In one embodiment, the retention rate of tensile strength (tensile strength measured in accordance with ISO 527-1, 2) of the molded product of this embodiment after storage for 50 hours under humid heat conditions of 121°C, 100% RH, and 2 atmospheres ((tensile strength after storage (MPa) / tensile strength before storage (MPa)) × 100 (%)) is preferably 65% or more, more preferably 69% or more, and even more preferably 70% or more.

[Application]
The molded article obtained from the resin composition according to the present embodiment has excellent wet heat resistance and good mechanical strength, and can be suitably used for applications such as case parts and vehicle door modules.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following description.

The following materials were used as raw materials for the resin composition.
<Polyolefin resin (A)>
Resin (A1): Propylene homopolymer (PP homopolymer, manufactured by SunAllomer Co., Ltd., product name "PMB02A").
Resin (A2-1): Maleic anhydride modified polypropylene resin (a2) (product name "Modic P908" manufactured by Mitsubishi Chemical Corporation, acid concentration (v1): 0.11 moL/kg).
Resin (A2-2): Maleic anhydride modified polypropylene resin (a2) (SK functional Polymers product name "OREVAC CA100", acid concentration (v1): 0.11 moL / kg).
<Regenerated Cellulose Fiber (B)>
- Solvent-process regenerated cellulose fiber (average fiber diameter (long diameter) 11 μm).
<Epoxy Compound (C)>
Epoxy compound (C-1): epoxidized soybean oil (product name "Adekacizer O-130P" manufactured by ADEKA CORPORATION, epoxy group concentration (f1): 4.2 moL/kg).
Epoxy compound (C-2): bisphenol type epoxy compound (bisphenol A type epoxy compound (manufactured by Mitsubishi Chemical Corporation, product name "jER (registered trademark) 1004K", epoxy group concentration (f1): 1.0 moL/kg)).
Epoxy compound (C-3): epoxy group-containing copolymer (ethylene-glycidyl methacrylate methyl acrylate (manufactured by Sumitomo Chemical Co., Ltd., product name "BONDFAST 7L", epoxy group concentration (f1): 0.2 moL/kg)).
<Other ingredients>
Antioxidant (1): Hindered phenol-based antioxidant (manufactured by BASF Japan Ltd., product name "Irganox (registered trademark) 1010").
Antioxidant (2): Phosphorus-based antioxidant (manufactured by BASF Japan Ltd., product name "Irgafos (registered trademark) 168").
Weather resistance agent: hindered amine light stabilizer (manufactured by BASF Japan Ltd., product name "Tinuvin (registered trademark) 111FD").

[Example 1]
66.6% by mass of resin (A1), 2.1% by mass of resin (A2-1), 0.08% by mass of epoxy compound (C-1), 0.21% by mass of antioxidant (1), 0.11% by mass of antioxidant (2) and 0.11% by mass of weather resistance agent were mixed and charged into a twin-screw extruder, and then melt-kneaded at a cylinder temperature of 260 ° C. to obtain a molten mixture. The regenerated cellulose fiber (B) was passed through a crosshead die and impregnated into a fiber bundle aligned in the length direction so that the regenerated cellulose fiber (B) was 30% by mass. Thereafter, the resin composition of Example 1 in the form of pellets was obtained by shaping with a shaping nozzle at the crosshead die outlet, shaping with a shaping roll, and cutting to a length of 7 mm with a pelletizer. The ratio (R) of the resin composition was 1.4.

Next, the resin composition (pellets) of Example 1 was injection molded under the following conditions to obtain a molded article (ISO tensile test piece). The obtained molded article was measured for various mechanical strengths under the following conditions. In addition, the moist heat resistance was measured under the following conditions.
(Molding conditions)
Molding machine: manufactured by Shibaura Machine Co., Ltd., product name "EC40".
Test specimen: ISO tensile test specimen.
Molding temperature: 200℃.
Mold temperature: 60°C.

<Evaluation of mechanical strength>
Using the obtained ISO tensile test pieces, the tensile strength (TS) and tensile elongation (TE) were measured in accordance with ISO 527-1 and 2. The tensile strength was evaluated according to the following evaluation criteria.
(Evaluation Criteria)
Excellent: The tensile strength is 90 MPa or more.
Good: The tensile strength is 80 MPa or more and less than 90 MPa.
Unacceptable: The tensile strength is less than 80 MPa.

<Evaluation of wet heat resistance>
The obtained ISO tensile test specimen was stored for 50 hours under the conditions of 121°C, 100% RH, and 2 atm. Thereafter, the tensile strength was measured under the same conditions as the above-mentioned mechanical strength evaluation. Furthermore, the tensile strength retention rate was calculated from the tensile strength (MPa) after the wet heat test and the tensile strength (MPa) before the wet heat test.
Tensile strength retention rate (%)=(tensile strength after wet heat test (MPa))/(tensile strength before wet heat test (MPa))×100
Furthermore, the wet heat resistance was evaluated according to the following evaluation criteria.
(Evaluation Criteria)
Excellent: Tensile strength retention is 70% or more.
Good: The tensile strength retention is 65% or more and less than 70%.
Unacceptable: Tensile strength retention is less than 65%.

[Examples 2 to 5 and Comparative Examples 1 to 6]
A resin composition was prepared under the same conditions as in Example 1, except that the composition of the resin composition was as shown in Table 1. A molded article was prepared from the obtained resin composition under the same conditions as in Example 1. The obtained molded article was evaluated for mechanical strength and moist heat resistance under the same conditions as in Example 1. The results are shown in Table 1.

As shown in Table 1, the molded articles of Examples 1 to 5 obtained from the resin composition satisfying the constitution of this embodiment were excellent in moist heat resistance and also had good mechanical strength. On the other hand, the molded articles of Comparative Examples 1 to 3 obtained from the resin composition not containing the epoxy compound (C) had good mechanical strength, but had low tensile strength retention and were poor in moist heat resistance. In addition, the molded article of Comparative Example 4 obtained from the resin composition containing the epoxy compound (C) but not the resin (A2) had good moist heat resistance but was poor in mechanical strength. Furthermore, in Comparative Examples 5 and 6 in which the ratio (R) of the resin composition was less than 0.9, the results also showed poor moist heat resistance.
From the above results, it was found that the resin composition according to this embodiment is excellent in moist heat resistance and can provide a molded article having good mechanical strength.

The molded article obtained from the resin composition according to this embodiment has excellent resistance to moist heat and good mechanical strength. Such molded articles can be suitably used for applications such as case parts and vehicle door modules.

Claims (10)

A resin composition comprising:
The resin composition comprises
A polyolefin resin (A) including a polypropylene resin (A1) and an acid-modified polypropylene resin (A2) which is at least one resin selected from a maleic acid-modified polypropylene resin (a1) and a maleic anhydride-modified polypropylene resin (a2) and has an acid concentration (in terms of maleic anhydride) (v1) of 0.01 to 0.5 moL/kg;
Regenerated cellulose fibers (B);
and an epoxy compound (C) having an epoxy group concentration (f1) of 0.1 to 6.0 mol/kg;
The content of the polyolefin resin (A) is 25 to 90 mass% and the content of the regenerated cellulose fiber (B) is 5 to 70 mass% relative to the total mass of the resin composition,
A resin composition, wherein the ratio (R) of an epoxy group concentration to an acid concentration in the resin composition, represented by the following formula (1), is 0.9 or more:

The resin composition according to claim 1, comprising a polyolefin resin-impregnated regenerated cellulose fiber bundle (B1) in which the regenerated cellulose fiber (B) is aligned in the length direction and impregnated with a mixture of the polyolefin resin (A) and the epoxy compound (C). The resin composition according to claim 1 or 2, wherein the epoxy compound (C) comprises at least one compound selected from the group consisting of epoxidized oils and fats, epoxy group-containing copolymers, bisphenol-type epoxy compounds, and epoxysilane compounds. The resin composition according to claim 1 or 2, wherein the ratio of the acid-modified polypropylene resin (A2) to the total mass of the polyolefin resin (A) is 0.5 to 5 mass%. A resin composition according to claim 1 or 2, wherein the content of the polyolefin resin (A) is 25 to 90 mass%, the content of the regenerated cellulose fiber (B) is 5 to 70 mass%, and the content of the epoxy compound (C) is 0.05 to 5 mass%, relative to the total mass of the resin composition. The resin composition according to claim 1 or 2, wherein the acid-modified polypropylene resin (A2) contains the maleic anhydride-modified polypropylene resin (a2). The resin composition according to claim 1 or 2, wherein the epoxy compound (C) comprises at least one compound selected from the group consisting of an epoxy group-containing copolymer and a bisphenol type epoxy compound. A resin composition according to claim 1 or 2, wherein the average fiber length of the regenerated cellulose fiber (B) in the resin composition is 5 to 30 mm. A molded article made from the resin composition according to claim 1 or 2. A method for producing the resin composition according to claim 1 or 2,
The method includes obtaining a mixture of the polyolefin resin (A) and the epoxy compound (C), and blending the mixture with the regenerated cellulose fibers (B),
The method for producing a resin composition includes mixing the polyolefin resin (A) and the epoxy compound (C) so that the ratio (R) of an epoxy group concentration to an acid concentration in the finally obtained resin composition, which is represented by the following formula (1), is 0.9 or more.