JP6715686B2 - Fiber-reinforced resin composition and injection foam molding method - Google Patents

Description

The present invention relates to a polypropylene fiber reinforced resin composition and an injection foam molding method thereof.

Polypropylene resins are widely used as resin materials in various industrial fields such as daily necessities, the field of home appliances, the field of home appliances, and automobile parts because they are excellent in moldability, balance of physical properties, recycling characteristics, cost performance and the like. Further, in recent years, there has been a strong demand for weight reduction of automobile parts in order to improve fuel efficiency and reduce global warming gas, and in particular, the use of foam molded articles for interior parts is increasing. However, for automobile interior and exterior parts, further weight reduction and maintenance or improvement of mechanical properties are required. Therefore, there is a demand for the development of an injection foam molded article having a higher expansion ratio and excellent mechanical properties.

In automotive member applications, in order to meet the demand for weight reduction of resin parts, it has been required to secure the rigidity of members more than ever before. For this reason, injection foam moldings of propylene-based resin compositions containing fillers represented by various reinforcing fibers have come into the limelight. For example, Patent Document 1 discloses a method of molding an injection-foaming molded article for automobile parts by physically foaming after melting a fiber-reinforced polyolefin resin composition containing a polyolefin resin and an organic fiber.

Generally, foam molding methods are classified into two types: physical foaming and chemical foaming. Physical foaming is a method of dissolving air, carbon dioxide gas, nitrogen, or a volatile solvent pressurized in a cylinder of an injection molding machine into a resin. The chemical foaming is a method in which a chemical foaming agent is charged together with a base material from a hopper of an injection molding machine, and a gas such as carbon dioxide gas, nitrogen, water, or ammonia is mixed into a resin by thermal decomposition or chemical reaction.

In the case of the physical foaming used in Patent Document 1, in addition to gas preparation, a mechanism for dissolving the gas in the resin, a mechanism for maintaining pressure so that the gas does not escape from the resin before molding, and the like are required. .. Therefore, it is necessary to introduce a new injection molding machine or modify an existing injection molding machine, resulting in high costs such as initial investment and maintenance costs. From this point of view, there is a strong need for chemical foaming, which requires almost no initial investment.

Chemical foaming agents can also be broadly classified into two types, inorganic foaming agents and organic foaming agents, depending on their types. Inorganic chemical foaming agents that are baking soda or combined baking soda and citric acid have no irritating odor generated during decomposition, unlike organic chemical foaming agents whose main component is ADCA (azodicarbonamide). It is used in many fields including. However, when performing injection foam molding using a baking soda-based chemical foaming agent, it has been pointed out that the chemical foaming agent itself or its decomposition residue adheres to the molding die, degrading the quality of the foamed molded product. There is. Therefore, various methods have been proposed to eliminate such mold contamination. For example, Patent Document 2 discloses a method in which a small amount of an ethylene/(meth)acrylic acid copolymer is added to polyethylene and injection foam molding is performed in the presence of a mixture of sodium citrate salt and sodium bicarbonate. Patent Document 3 discloses a method in which a small amount of (meth)acrylic acid homopolymer is allowed to coexist in a propylene-based polymer and injection foaming is performed with a chemical foaming agent. However, in these patent documents, no study is made on a method of injection-foaming and molding a fiber-reinforced resin composition containing a reinforcing fiber by using a chemical foaming agent.

JP, 2011-189557, A JP 2004-285345 A JP, 2010-043161, A

When the present inventors perform injection foam molding of a resin composition containing reinforcing fibers by the method disclosed in Patent Documents 2 or 3, rust occurs on the surface of the mold due to long-term use of the mold, or It has been found that there is a problem that foreign matter bleeds out from the inside of the molded product when the injection foam molded product is stored for a long time under high temperature and high humidity conditions. The generation of rust on the surface of the mold may cause fatal damage to the molded product if a fine grain pattern is drawn on the surface of the cavity, even if the amount is small. That is, it is necessary to develop a fiber-reinforced injection foam molding using a chemical foaming agent, which does not cause deterioration of physical properties such as strength under high temperature and high humidity conditions and does not cause rust on the mold surface. ..

That is, an object of the present invention is to prevent rusting on the mold surface even when the mold is used for a long time when injection-foaming a propylene-based polymer containing a reinforcing fiber by using a chemical foaming agent, and It is an object of the present invention to provide a fiber-reinforced resin composition for injection foam molding, in which physical properties such as strength do not easily deteriorate even when the injection foam molded article is stored under high temperature and high humidity, and an injection foam molding method thereof.

As a result of intensive studies to achieve the above object, the present inventors have found that a specific amount of a polar resin (B) and a specific type and a specific amount of chemical foaming are added to a propylene polymer (A) which is a base resin. It was found that it is very effective to mix the agent (F) and injection foam molding, and completed the present invention. That is, the gist of the present invention is as follows.

（式（１）において、一つの酸無水物基は二個のカルボキシル基に等価であるとした） [1] a propylene-based polymer (A),
A polar resin (B) containing a carboxyl group and/or an acid anhydride group,
A chemical foaming agent (F) containing a carbonate (f),
Including reinforcing fiber (R),
A fiber-reinforced resin composition for injection foam molding, which satisfies the following formula (1).

(In the formula (1), one acid anhydride group is equivalent to two carboxyl groups)

[2] The polar resin (B) containing a carboxyl group and/or an acid anhydride group is ethylene/acrylic acid copolymer, ethylene/methacrylic acid copolymer, polyacrylic acid, polymethacrylic acid and maleic anhydride modified polypropylene. The fiber-reinforced resin composition according to the above [1], which is one or more resins selected from the group consisting of:
[3] The above-mentioned [1] or [2], wherein the carbonate (f) is one or more compounds selected from the group consisting of ammonium carbonate, alkali metal carbonate, ammonium hydrogencarbonate and alkali metal hydrogencarbonate. Fiber-reinforced resin composition.

[4] The fiber reinforced resin composition according to the above [3], wherein the carbonate (f) is sodium hydrogen carbonate.
[5] The fiber-reinforced resin composition according to any one of [1] to [4], wherein the reinforcing fiber (R) is a glass fiber (R1).
[6] The fiber-reinforced resin composition according to any one of [1] to [4], wherein the reinforcing fiber (R) is a carbon fiber (R2).
[7] The fiber-reinforced resin composition according to any one of [1] to [6], wherein the content of the reinforcing fiber (R) is 10 to 50 mass% with respect to the total amount of the fiber-reinforced resin composition.
[8] Any of the above-mentioned [1] to [7], wherein the amount of the propylene-based polymer (A) is 70 to 99 parts by weight in a total of 100 parts by weight of the propylene-based polymer (A) and the polar resin (B). A fiber-reinforced resin composition as described in.

[9] The volume of the cavity is smaller than the total volume of the melt of the fiber-reinforced resin composition according to any one of the above [1] to [8]. A step of injecting a melt of the resin composition into the cavity, and
An injection foam molding method comprising a step of opening the mold up to the volume of the final molded body after the step.

According to the present invention, when injection-molding a polypropylene-based polymer containing a reinforcing fiber using a chemical foaming agent, rust is unlikely to occur on the mold surface even when the mold is used for a long period of time, and the injection is performed. It is possible to provide a fiber-reinforced resin composition for injection foam molding in which physical properties such as strength do not easily deteriorate even when the foam molded article is stored under high temperature and high humidity, and an injection foam molding method thereof.

Hereinafter, a chemical foaming agent (F) containing a propylene polymer (A), a polar resin (B), a carbonate (f) and a reinforcing fiber (constituting the fiber reinforced resin composition for injection foam molding of the present invention, R) will be described. In the following description, the respective components may be abbreviated as component (A), component (B), component (f), component (F) and component (R), respectively.

<Propylene polymer (A)>
The propylene-based polymer (A) used in the present invention may be a homopolymer of propylene or a copolymer of propylene and another monomer. In particular, a homopolymer of propylene, a random copolymer or a block copolymer of propylene and ethylene and at least one α-olefin selected from α-olefins having 4 to 20 carbon atoms are preferable. The content of the propylene-derived skeleton in the random copolymer is usually 90 to 99 mol%, preferably 92 to 98 mol%. The skeleton content derived from propylene in the block copolymer is usually 70 to 99 mol %, preferably 75 to 98 mol %.

Specific examples of the α-olefin having 4 to 20 carbon atoms include 1-butene, 2-methyl-1-propene, 2-methyl-1-butene, 3-methyl-1-butene, 1-pentene and 1-butene. Hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl- 1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, ethyl-1-pentene, trimethyl-1-butene, methylethyl-1-butene, 1-octene, methyl-1-pentene, ethyl -1-hexene, dimethyl-1-hexene, propyl-1-heptene, methylethyl-1-heptene, trimethyl-1-pentene, propyl-1-pentene, diethyl-1-butene, 1-nonene, 1-decene, Examples thereof include 1-undecene and 1-dodecene. Among these, α-olefins such as 1-butene, 1-pentene, 1-hexene, and 1-octene can be preferably used.

The melt flow rate (MFR) of the propylene-based polymer (A) obtained according to ASTM D1238 at 230° C. and a load of 2.16 kg is preferably 0.1 to 500 g/10 minutes, more preferably 0.2. ~400 g/10 min, particularly preferably 0.3-300 g/10 min. The lower limit of the MFR range is significant in terms of injection foaming moldability, appearance and the like. Further, the upper limit value is significant in terms of strength, wear resistance, etc. of the molded product.

The propylene polymer (A) is preferably an isotactic polypropylene polymer. The isotactic propylene-based polymer is a propylene-based polymer having an isotactic pentad fraction of 0.9 or more, preferably 0.95 or more, which is determined by an NMR method. The propylene polymer (A) may be prepared using a Ziegler-Natta catalyst or may be prepared using a metallocene catalyst.

<Polar resin (B)>
The polar resin (B) used in the present invention is a polar resin containing a carboxyl group and/or an acid anhydride group.

As the polar resin (B) containing a carboxyl group, one or more compounds selected from ethylene/acrylic acid copolymers, ethylene/methacrylic acid copolymers, polyacrylic acid and polymethacrylic acid can be preferably used. These polymers can be produced by a known method. The acrylic acid content of the ethylene/acrylic acid copolymer is usually 5.0 to 40% by mass, preferably 10 to 30% by mass. The methacrylic acid content of the ethylene/methacrylic acid copolymer is usually 2.0 to 30% by mass, preferably 5.0 to 25% by mass.

As the polar resin (B) containing an acid anhydride group, a polyolefin polymer modified with an unsaturated carboxylic acid anhydride can be preferably used. Specific examples of unsaturated carboxylic acid anhydrides include acid anhydrides such as maleic acid, fumaric acid, itaconic acid, citraconic acid, sorbic acid, mesaconic acid and angelic acid. Among them, maleic anhydride is preferable from the viewpoint of easy availability and easy handling. The amount of the acid anhydride group contained in the polar resin (B) is usually 0.01 to 20% by mass, preferably 0.02 to 10% by mass, and more preferably 0.1 to 5% by mass.

As the polar resin (B) containing a carboxyl group and/or an acid anhydride group, ethylene/acrylic acid copolymer, ethylene/methacrylic acid copolymer, polyacrylic acid, polymethacrylic acid and maleic anhydride modified polypropylene are particularly preferable. It is preferable to use at least one resin selected from the group consisting of

<Chemical foaming agent (F)>
The chemical foaming agent (F) used in the present invention is a chemical foaming agent containing a carbonate (f). Specific examples of the carbonate (f) include ammonium carbonate, alkali metal carbonate, ammonium hydrogen carbonate, and alkali metal hydrogen carbonate. Of these, alkali metal hydrogen carbonates are preferable, and sodium hydrogen carbonate (baking soda) is particularly preferable. The decomposition type chemical foaming agent containing baking soda may contain a small amount of a foaming aid such as citric acid. The content of the carbonate (f) contained in the chemical foaming agent (F) is usually 5 to 50% by mass, preferably 10 to 40% by mass. A commercially available product can be used as it is as the chemical foaming agent (F). The chemical foaming agent (F) may be used as a masterbatch with the component (A) or the component (B).

<Reinforcing fiber (R)>
The reinforcing fiber (R) used in the present invention is not particularly limited, and various known reinforcing fibers can be used. Generally, it is preferable to use at least one fiber selected from glass fiber (R1) and carbon fiber (R2).

As the glass fiber (R1), for example, glass fibers such as E glass, C glass, S glass, and alkali glass can be melt-spun to form filaments. As the raw material of the glass fiber (preferably long glass fiber), for example, a continuous glass fiber bundle commercially available as glass roving can be used. The glass fiber (R1) preferably has an average fiber diameter of 3 to 300 μm and a filament focusing number of 400 to 10,000, more preferably an average fiber diameter of 5 to 25 μm, and a filament focusing number of 1,000 to 6,000, more preferably an average fiber. It is particularly preferable that the diameter is 5 to 20 μm and the number of filaments to be bundled is 3,000 to 5,000.

Regarding the fiber length of the glass fiber (R1), the fiber length in the pellet is usually 0.5 to 20 mm, preferably 1 to 12 mm in the state of being pelletized by melt-kneading with the resin composition. The glass fibers (R1) may be long fibers such as continuous fibers or short fibers such as chopped strands.

The surface of the glass fiber (R1) may be provided with a functional group by various known surface treatment methods such as electrolytic treatment and sizing agent treatment. A sizing agent is preferably used for the surface treatment, and a sizing agent containing a coupling agent is particularly preferably used. When the glass fiber (R1) thus surface-treated is used, the adhesiveness with polypropylene is improved, and a molded product having excellent strength and appearance can be obtained. Examples of the sizing agent include those containing a coupling agent as described in JP-A-2003-253563. The coupling agent can be appropriately selected from so-called silane coupling agents such as aminosilane and epoxysilane, and coupling agents known as titanium coupling agents.

Various known carbon fibers can be used as the carbon fibers (R2). Specific examples thereof include carbon fibers of polyacrylonitrile type, rayon type, pitch type, polyvinyl alcohol type, regenerated cellulose, pitch type manufactured from mesophase pitch, and the like. The carbon fibers (R2) may be long fibers or short fibers such as chopped strands. A continuous fiber bundle can be used as a raw material for long fibers, which is commercially available as tow. Usually, the average fiber diameter is 3 to 30 μm, and the filament converging number is 500 to 80,000, and preferably the average fiber diameter is 4 to 10 μm and the converging number is 12,000 to 50,000. Regarding the fiber length of the carbon fiber (R2), in the state of being pelletized by melt-kneading with the resin composition, the fiber length in the pellet is usually 0.5 to 20 mm, preferably 0.5 to 12 mm.

The carbon fibers (R2) are preferably carbon fiber bundles bundled with a sizing agent (sizing agent). Specifically, it is preferable to use a large number of carbon fibers (R2) integrally bound with a sizing agent. The sizing agent constituting the carbon fiber bundle has a repeating unit represented by the following formula (I) and a formula (II) below, for example, as described in Japanese Patent No. 5650117, from the viewpoint of increasing mechanical strength. It is preferable to use a sizing agent composed of a copolymer containing a repeating unit represented by: The amount of the sizing agent attached is preferably 0.1 to 6.0 parts by mass, and more preferably 0.2 to 5.0 parts by mass with respect to 100 parts by mass of the carbon fiber.

(In formulas (I) and (II), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an aryl group having 6 to 10 carbon atoms. Represents an alkoxy group having 1 to 4 carbon atoms, an alkoxycarbonyl group having 1 to 18 carbon atoms or an alkylcarboxyl group having 1 to 17 carbon atoms, and R ³ and R ⁴ each independently represent a hydrogen atom or a C 1 to 6 carbon atom. Represents an alkyl group, and R ⁵ represents an alkylene group having 1 to 12 carbon atoms, a cycloalkylene group having 5 to 17 carbon atoms, an arylene group having 6 to 12 carbon atoms, an arylalkylene group having 7 to 12 carbon atoms, or 4 to 12 carbon atoms. The polyoxyalkylene group of 30. R ^{1 to} R ⁵ may be the same or different for each repeating unit.)

The fiber-reinforced resin composition of the present invention may use a reinforcing fiber (R) other than the glass fiber (R1) and the carbon fiber (R2) as long as the object of the present invention is not impaired. Examples of such reinforcing fibers include organic fibers. Examples of the organic fibers include polyethylene fibers, polypropylene fibers, aramid fibers, polyester fibers, vinylon fibers, organic fibers such as cotton, hemp, silk and bamboo. You may use these organic fibers in combination of 2 or more types. In the present invention, the reinforcing fiber (R) may be blended in the form of a masterbatch such as a masterbatch with the component (A) and a masterbatch with the component (B).

The content of the reinforcing fiber (R) in the entire reinforcing fiber resin composition of the present invention is usually 5 to 50% by mass, preferably 10 to 50% by mass, more preferably 10 to 45% by mass, and particularly preferably 10 to 10. It is 40 mass %. When the content of the reinforcing fiber (R) is less than 5% by mass, the effect of improving the physical properties by adding the fiber is small, and when it exceeds 50% by mass, the effect of reducing the weight becomes small, which is not preferable.

<Other ingredients>
The reinforcing fiber resin composition of the present invention may further contain other components such as fatty acid amide, fatty acid metal salt, antioxidant, weathering stabilizer, light stabilizer, ultraviolet absorber, pigment, dye, plasticizer, if necessary. Additives such as lubricants, flame retardants and inorganic fillers can be added. Specific examples of the inorganic filler include silica, alumina, calcium carbonate, talc, clay, zeolite and carbon black.

Further, a polymer other than the component (A) and the component (B) may be blended within a range not impairing the object of the present invention. For example, olefin polymers such as ethylene/(meth)acrylic acid ester copolymers, polyethylene, and ethylene/α-olefin copolymers, and these for the purpose of improving physical properties such as impact resistance of the injection-foam molded article. An acid-modified product obtained by grafting an unsaturated carboxylic acid such as maleic anhydride or its anhydride onto the polymer can also be blended.

<Fiber-reinforced resin composition>
The fiber-reinforced resin composition of the present invention is a resin composition containing the component (A), the component (B), the component (F) and the component (R) described above. In the present invention, it is important to determine the blending amounts of the component (B) and the component (F) according to the following formula (1), preferably the following formula (2), and more preferably the following formula (3). By satisfying these equations, it is possible to effectively suppress the mold contamination during injection foam molding and the deterioration of physical properties such as strength at high temperature and high humidity.

In the above formulas (1) to (3), one acid anhydride group is equivalent to two carboxyl groups. That is, when an acid anhydride group (for example, the acid anhydride group of the component (B)) is present in the composition, one acid anhydride group is a group composed of two carboxyl groups, The total number of carboxyl groups in the composition was calculated, assuming that one anhydride group corresponds to two carboxyl groups. The unit of the amount of carbonate (f) and the amount of carboxyl in the composition is mol.

In the fiber-reinforced resin composition, the amount of the propylene-based polymer (A) is preferably 70 to 99 parts by weight, more preferably 75, based on 100 parts by weight of the total of the propylene-based polymer (A) and the polar resin (B). ˜97% by mass.

<Method for producing fiber-reinforced resin composition>
The method for producing the fiber-reinforced resin composition of the present invention is not particularly limited. For example, the component (A), the component (B), the component (F) and the component (R), and optionally other components are melt-kneaded. Or by dry blending. Examples of the apparatus used for kneading include a single-screw extruder, a twin-screw extruder, a Banbury mixer, and a hot roll.

The temperature of melt kneading (heat treatment) is preferably 170 to 250° C., and the time of melt kneading is preferably 20 seconds to 20 minutes. The respective components may be kneaded at the same time or may be divided. As a method for producing the fiber reinforced resin composition, for example, a method including a step of uniformly premixing the respective components with a mixing device such as a tumbler and a step of melt-kneading the premix is preferable. The fiber-reinforced resin composition after melt-kneading is usually used in the form of pellets as a raw material for injection foaming. On the other hand, when the dry blending method is adopted, it is preferable that the dry blending method is directly passed through a molding machine such as an injection molding machine without passing through an extruder.

<Injection foam molding method>
The fiber-reinforced resin composition of the present invention is used for injection foam molding. The injection foam molding method is not limited, and known injection molding conditions and known injection molding apparatuses may be used. Specifically, the injection temperature (cylinder temperature) is usually 180 to 250° C., and the injection molding time is usually 10 seconds to 5 minutes.

In particular, a step of injecting a melt of the resin composition into the cavity of the mold in a closed state so that the volume of the cavity is smaller than the total volume of the melt of the fiber reinforced resin composition, and An injection foam molding method having a step of opening the mold to the volume of the final molded body after the above step, a so-called core back method is preferable.

Further, a decorative foam molding can be obtained by laminating a skin material by a method such as insert molding or adhesion. As the skin material, known materials can be used. Specific examples of the skin material include a woven cloth, a non-woven cloth, a knitted cloth, a film made of a thermoplastic resin or a thermoplastic elastomer, and a sheet. Further, a composite skin material obtained by laminating sheets of polyurethane, rubber, thermoplastic elastomer, etc. on the skin material may be used. Further, a cushion layer may be further provided on the skin material.

<Applications of foamed molded products>
The foamed molded product obtained by injection-foaming and molding the fiber-reinforced resin composition of the present invention is useful for various applications. For example, it can be suitably used for automobile parts such as automobile interior parts and exterior parts, two-wheeled vehicle parts, furniture and parts for electric appliances. Among them, those for automobile parts are preferable, and those for automobile interior parts are more preferable. Examples of automobile interior parts include instrumental panels, trims, door panels, side protectors, console boxes, column covers and the like. Examples of automobile exterior parts include bumpers, fenders, wheel covers, and the like. Examples of motorcycle parts include cowlings and muffler covers.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The components used in the examples and comparative examples are as follows.

<Propylene polymer (A)>
“H-PP”: homopolypropylene (MFR (230° C., 2.16 kg load) measured according to ASTM D1238E, trade name J137G manufactured by Prime Polymer Co., Ltd.=30 g/10 min, isotactic pentad fraction mm mm = 97.8%)

<Polar resin (B)>
"B1": ethylene/methacrylic acid copolymer (manufactured by Mitsui/DuPont Polychemical, trade name Nucrel (registered trademark) N1525, methacrylic acid content=15% by mass)
"B2": ethylene-acrylic acid copolymer (trade name: Primacol (registered trademark) 59801, manufactured by Dow Chemical Company, acrylic acid content = 20 mass%)
"B3": polyacrylic acid (Nippon Shokubai Co., Ltd., trade name Aqualic (registered trademark) AS58)
"B4": Maleic anhydride-modified polypropylene (manufactured by Chemtura, trade name POLYBOND (registered trademark) 3200, MFR measured according to ASTM D1238E (230°C, 2.16 kg load) = 250 g/10 minutes, maleic anhydride Derived structural unit content = 2.2% by mass)

<Chemical foaming agent (F)>
"H3510": baking soda (manufactured by Eiwa Chemical Co., Ltd., trade name H3510, sodium hydrogen carbonate content=25% by mass)

<Reinforcing fiber (R)>
"Glass fiber": glass roving (Nippon Electric Glass Co., Ltd., trade name T-477N), fiber diameter 17 μm

<Other ingredients>
"Black MB": PT-RM H1016-45 [H] manufactured by Dainichiseika Co., Ltd.

[Examples 1 to 6 and Comparative Examples 1 to 6]
Propylene polymer (A), polar resin (B) and reinforcing fiber (R) are blended, and 50% GF master is prepared in the same manner as the long fiber reinforced pellet manufacturing method described in WO 2005/075554. A batch (long fiber reinforced pellet) was prepared. Specifically, polypropylene (A) and polar resin (B) are evenly mixed by a tumbler, supplied from a 50 mφ extruder set at 280° C. to an impregnation tank, and then reinforcing fiber (R) is placed in the impregnation tank. Was fed to the rod in the tank to open the fiber, impregnated with the molten resin, pulled out from the impregnation tank, cooled, and pelletized to obtain long fiber reinforced pellets having a fiber amount of 50% by mass.

Further, this long fiber reinforced pellet was uniformly mixed with polypropylene (A), polar resin (B), chemical foaming agent (F) and black MB with a tumbler. The blending ratio (parts by mass) of each component shown in Tables 1 and 2 is polypropylene (A), polar resin (B) and chemical foaming agent (F) mixed at this stage, and the propylene-based resin contained in the long fiber reinforced pellets. It is a ratio based on the total amount of the polymer (A), the polar resin (B) and the reinforcing fiber (R). Then, using an injection molding machine (manufactured by Niigata Machinetex, trade name NN220α), a cylinder temperature of 240°C, a mold temperature of 40°C, an injection time-a holding time of 20 seconds (primary filling time: 3 seconds), a cooling time. Injection-foam molding was performed under the conditions of a holding pressure of 60 MPa for 25 seconds to obtain a test piece. Then, the following measurements and evaluations were performed. The results are shown in Tables 1 and 2.

(1) Amount of carbonate (f)/amount of carboxyl group Content of methacrylic acid-derived skeleton of component (B1)=15% by mass, content of skeleton derived from acrylic acid of component (B2)=20% by mass, acrylic of component (B3) [Amount of carbonate (f)/amount of carboxyl group] was calculated with the acid-derived skeleton content=100% by mass and the component 30456 sodium hydrogen carbonate (baking soda) content=25% by mass.

Of the above components, the manufacturer's reported values for the carboxyl group content in ethylene/methacrylic acid copolymer (B1) and ethylene/acrylic acid copolymer (B2) and the carboxyl group content in polyacrylic acid (B3) Was used. Regarding the content of sodium hydrogen carbonate in the chemical foaming agent (H3510), the chemical foaming agent was decomposed by dry (500° C.), dissolved in dilute acid, and then diluted to a fixed volume and diluted to obtain a test solution, which was then analyzed by ICP emission spectrometry. It was calculated by the amount of sodium determined by.

For the maleic anhydride-modified polypropylene (B4), 2 g of the resin was taken, completely dissolved in 500 ml of boiling p-xylene by heating, then cooled and poured into 1200 ml of acetone, and the precipitate was filtered and dried to obtain a polymer. A purified product was obtained. Then, the purified polymer product was hot pressed to produce a film having a thickness of 20 μm. The infrared absorption spectrum (near 1780 cm ⁻¹ ) of this film was measured to measure the content of acid anhydride groups. The carboxyl group (equivalent) in the maleic anhydride-modified polypropylene (B4) was calculated as being twice the acid anhydride group (equivalent).

(2) Bending Strength of Foam Molded Article The bending test was carried out under the following conditions according to JIS K7171.
Test piece shape: Strip test piece (100 mm x 25 mm x 2 mmt)
Test temperature: 23℃
Distance between fulcrums: 60 mm
Test speed: 2mm/min

(3) Bending strength of foamed molded product after high temperature and high humidity treatment and its retention rate The bending strength ( ₀ hr) measured under the above conditions is S _0, and the high temperature and high humidity tank adjusted to 60° C.×90% RH The bending strength (500 hr) measured on the test piece after being stored for 500 hours under the same conditions was S _1, and S ₁ /S ₀ was calculated as the bending strength retention rate.

(4) Evaluation method of mold rust that occurs during molding Using a mold of 40 mm × 70 mm × 3.2 mm and an injection molding machine (Toshiba Kikai Co., Ltd., trade name EC40), molding temperature 240°C, mold temperature : 120 shots of short shots were continuously molded under the condition of 40° C., and then the presence or absence of rust in the mold near the flow front was visually determined based on the following criteria.
"○": No rust was observed.
“A”: A slight rust-like foreign substance was recognized.
“×”: Rust was clearly observed.

As is clear from Table 1 and Table 2, in Examples 1 to 7, the foamed molded articles after the high temperature and high humidity treatment at 60° C.×90% RH had a high flexural strength retention rate, that is, a decrease in flexural strength occurred. It was difficult. Further, even when 120 shots of short shots were continuously formed, no rust was observed on the mold.

On the other hand, in Comparative Examples 1 and 3, since the compounding ratio (equivalent ratio) of the carbonate (f) to the total amount of carboxyl groups in the composition was too low, rusting of the mold occurred. In Comparative Examples 2, 4 and 5, the above-mentioned compounding ratio was too high, so the bending strength was significantly reduced. In Comparative Example 6, since the compounding ratio was extremely low, the bending strength was significantly reduced.

The foamed molded product obtained by injection-foaming and molding the fiber-reinforced resin composition of the present invention is useful for various applications. For example, it can be suitably used for automobile parts such as automobile interior parts and exterior parts, two-wheeled vehicle parts, parts for furniture and electric products, and the like.

Claims (9)

A propylene-based polymer (A),
A polar resin (B) containing a carboxyl group and/or an acid anhydride group,
A chemical foaming agent (F) containing a carbonate (f),
Including reinforcing fiber (R),
A fiber-reinforced resin composition for injection foam molding, which satisfies the following formula (1).

(In the formula (1), one acid anhydride group is equivalent to two carboxyl groups) A group in which the polar resin (B) containing a carboxyl group and/or an acid anhydride group is composed of ethylene/acrylic acid copolymer, ethylene/methacrylic acid copolymer, polyacrylic acid, polymethacrylic acid and maleic anhydride modified polypropylene. The fiber-reinforced resin composition according to claim 1, which is one or more resins selected from the following. The fiber-reinforced resin composition according to claim 1 or 2, wherein the carbonate (f) is one or more compounds selected from the group consisting of ammonium carbonate, alkali metal carbonate, ammonium hydrogen carbonate, and alkali metal hydrogen carbonate. .. The fiber reinforced resin composition according to claim 3, wherein the carbonate (f) is sodium hydrogen carbonate. The fiber-reinforced resin composition according to any one of claims 1 to 4, wherein the reinforcing fiber (R) is a glass fiber (R1). The fiber-reinforced resin composition according to any one of claims 1 to 4, wherein the reinforcing fiber (R) is a carbon fiber (R2). Content of reinforcing fiber (R) is 10-50 mass% with respect to the fiber-reinforced resin composition whole quantity, The fiber-reinforced resin composition in any one of Claims 1-6. The fiber reinforced according to any one of claims 1 to 7, wherein the amount of the propylene polymer (A) is 70 to 99 parts by mass in 100 parts by mass of the total of the propylene polymer (A) and the polar resin (B). Resin composition. The resin composition in the cavity of the mold in a closed state such that the volume of the cavity is smaller than the total volume of the melt of the fiber reinforced resin composition according to any one of claims 1 to 8. Injecting a melt of the object, and
An injection foam molding method comprising a step of opening the mold up to the volume of the final molded body after the step.