Flame-retardant cellulose fiber composite resin composition

Abstract

Provided is a flame-retardant cellulose fiber composite resin composition capable of suppressing reduction in fluidity and maintaining good moldability even when a high concentration of cellulose fibers is added. The flame-retardant cellulose fiber composite resin composition contains a main component resin, cellulose fibers, and a phosphorus flame retardant. The decomposition temperature TFR of the phosphorus flame retardant is TCeF-30°C or higher and TCeF+30°C or lower, wherein TCeF is the decomposition temperature of the cellulose fibers.

Description

Flame-retardant cellulose fiber composite resin composition

[0001] The present disclosure relates to a flame-retardant cellulose fiber composite resin composition and a flame-retardant cellulose fiber composite resin molded article.

[0002] So-called "general-purpose plastics" such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) are relatively inexpensive, lightweight (a fraction of the weight of metals or ceramics), and easy to process, such as molding. For these reasons, general-purpose plastics are used as materials for a variety of everyday items such as bags, various types of packaging, various types of containers, and sheets, as well as industrial parts such as automobile parts and electrical parts, and for daily necessities and miscellaneous goods.

[0003] However, general-purpose plastics have drawbacks such as insufficient mechanical strength, and therefore do not have sufficient properties required for materials used in various industrial products, including mechanical products such as automobiles, and electrical, electronic, and information products, and the range of their application is currently limited.

[0004] On the other hand, so-called "engineering plastics" such as polyacetal (POM), polyamide (PA), polycarbonate (PC), and fluororesin have excellent mechanical properties and are used in various industrial products, including mechanical products such as automobiles, and electrical, electronic, and information products. However, engineering plastics have problems such as being expensive, difficulty in monomer recycling, and a large environmental impact.

[0005] Therefore, there is a demand for significant improvements in the material properties (mechanical strength, etc.) of general-purpose plastics. A known method for improving the material properties of general-purpose plastics is to produce composite resins by blending two or more types of resins or additives such as fillers. In particular, fibrous fillers such as natural fibers, glass fibers, and carbon fibers are used to improve mechanical strength. Among these, organic fibrous fillers such as cellulose have recently attracted attention as reinforcing fibers because they are inexpensive and environmentally friendly when disposed of.

[0006] Incidentally, some components in automobiles, office automation equipment, and electrical, electronic, and information products require flame retardancy. To impart flame retardancy to resin components, a large amount of flame retardant must be added, which reduces fluidity and molding processability. Furthermore, halogen-based flame retardants have traditionally been used as flame retardants due to their high flame retardancy. However, because they generate halogen-based toxic gases upon combustion, non-halogen flame retardants are being considered. In Patent Document 1, an inorganic flame retardant is supported on the tracheids of cellulose-based powder, allowing a large amount of flame retardant to be added without reducing molding processability, thereby imparting flame retardancy.

[0007] Japanese Patent Application Laid-Open No. 2001-64451

[0008] However, the composite resin described in Patent Document 1 requires the addition of a large amount of an inorganic flame retardant to impart flame retardancy, and therefore, when cellulose fibers are added at a high concentration, there is a problem that the fluidity decreases and molding becomes difficult. Even in the examples, the maximum amount of cellulose powder added is only 40% or less.

[0009] The present disclosure is intended to solve the above-mentioned conventional problems, and aims to provide a flame-retardant cellulose fiber composite resin composition that can suppress a decrease in fluidity and maintain good moldability even when cellulose fibers are added at a high concentration.

[0010] The flame-retardant cellulose fiber composite resin composition according to the present disclosure includes a base resin, cellulose fibers, and a phosphorus-based flame retardant, and has a decomposition temperature T ＦＲ is the decomposition temperature of cellulose fiber, T ＣｅＦ About T ＣｅＦ -30℃ or higher, T ＣｅＦ It is below +30°C.

[0011] According to the flame-retardant cellulose fiber composite resin composition of the present disclosure, the decomposition temperature T ＦＲ is the decomposition temperature of cellulose fiber, T ＣｅＦ About T ＣｅＦ -30℃ or higher, T ＣｅＦThe temperature is not higher than +30° C. Therefore, flame retardancy can be effectively imparted, and a cellulose fiber composite resin molding can be obtained using the cellulose fiber composite resin composition having high fluidity.

[0012] 1 is a schematic cross-sectional view showing the cross-sectional structure of a flame-retardant cellulose fiber composite resin composition according to Embodiment 1. 2 is Table 1 showing the conditions and measurement results in Examples 1 to 5 and Comparative Examples 1 to 3.

[0013] The flame-retardant cellulose fiber composite resin composition according to the first aspect includes a base resin, cellulose fibers, and a phosphorus-based flame retardant, and has a decomposition temperature T ＦＲ is the decomposition temperature of cellulose fiber, T ＣｅＦ About T ＣｅＦ -30℃ or higher, T ＣｅＦ It is below +30°C.

[0014] The cellulose fiber composite resin composition according to the second aspect is the cellulose fiber composite resin composition according to the first aspect, wherein the phosphorus-based flame retardant has a decomposition temperature T ＣｅＦ About T ＣｅＦ -30℃ or higher, T ＣｅＦ Decomposition temperature T below +30°C ＲＦ１ and a first phosphorus-based flame retardant having a decomposition temperature T ｐ About T ｐ -30℃ or higher, T ｐ Decomposition temperature T below +30°C ＲＦ２ and a second phosphorus-based flame retardant having the formula:

[0015] The flame-retardant cellulose fiber composite resin composition according to a third aspect may be the first or second aspect, wherein the phosphorus-based flame retardant has a phosphorus content of 5 mass % or more in the phosphorus compound.

[0016] The flame-retardant cellulose fiber composite resin composition according to a fourth aspect may be any one of the first to third aspects, in which the amount of cellulose fiber added is 10% by mass or more and 90% by mass or less.

[0017] The flame-retardant cellulose fiber composite resin composition according to a fifth aspect may be any one of the first to fourth aspects, in which the amount of the phosphorus-based flame retardant added is 1 mass % or more and 30 mass % or less.

[0018] The flame-retardant cellulose fiber composite resin composition according to a sixth aspect may be any one of the first to fifth aspects, in which the base resin has a melt flow index (MFR) of 10 g / 10 min or more.

[0019] The flame-retardant cellulose fiber composite resin composition according to a seventh aspect is the flame-retardant cellulose fiber composite resin composition according to any one of the first to sixth aspects, wherein the main resin is a polyolefin.

[0020] The flame-retardant cellulose fiber composite resin composition according to the eighth aspect may be any of the first to seventh aspects, further comprising an acid-modified polyolefin, and the mass ratio of the base resin to the acid-modified polyolefin may be 100:10 or more.

[0021] The flame-retardant cellulose fiber composite resin molding according to a ninth aspect may be any one of the first to eighth aspects, in which the aspect ratio of the cellulose fibers is 2 or more and the average fiber length is 50 μm or more.

[0022] A flame-retardant cellulose fiber composite resin composition according to a tenth aspect is the flame-retardant cellulose fiber composite resin composition according to any one of the first to ninth aspects, wherein the cellulose fibers may have a phosphorus-based flame retardant attached to the surface thereof.

[0023] The flame-retardant cellulose fiber composite resin molding according to an eleventh aspect is a cellulose fiber composite resin molding containing a base resin, cellulose fibers, and a phosphorus-based flame retardant, and the decomposition temperature T ＦＲ is the decomposition temperature of cellulose fiber, T ＣｅＦ About T ＣｅＦ -30℃ or higher, T ＣｅＦ It is below +30°C.

[0024] The flame-retardant cellulose fiber composite resin molding of the twelfth aspect may be the same as the eleventh aspect, in which the fiber length direction of the cellulose fibers in the skin layer on the surface side of the flame-retardant cellulose fiber composite resin molding is oriented at an angle of 0° or more and 30° or less relative to the surface of the flame-retardant cellulose fiber composite resin molding by 50% or more.

[0025] The method for producing a flame-retardant cellulose fiber composite resin molding according to the thirteenth aspect includes a mixing step for adhering a phosphorus-based flame retardant to cellulose fibers, a kneading step for kneading a main resin, cellulose fibers, and the phosphorus-based flame retardant to obtain a cellulose fiber composite resin composition, and a molding step for molding the cellulose fiber composite resin composition to obtain a cellulose fiber composite resin molding.

[0026] Hereinafter, a flame-retardant cellulose fiber composite resin composition and a cellulose fiber composite resin molded article according to embodiments will be described with reference to the accompanying drawings. In the following description, the same components are denoted by the same reference numerals and their description will be omitted where appropriate.

[0027] (Embodiment 1) <Flame-retardant cellulose fiber composite resin composition (molded article)> FIG. 1 is a schematic cross-sectional view showing the cross-sectional structure of a flame-retardant cellulose fiber composite resin composition (molded article) 10 according to embodiment 1. The flame-retardant cellulose fiber composite resin (molded article) 10 according to embodiment 1 includes a base resin 1, cellulose fibers 2, and a phosphorus-based flame retardant 3. As shown in FIG. 1, the flame-retardant cellulose fiber composite resin composition 10 has cellulose fibers 2 and a phosphorus-based flame retardant 3 dispersed in a matrix of the base resin 1, and the phosphorus-based flame retardant 3 is also present on the surface of the cellulose fibers 2. This flame-retardant cellulose fiber composite resin composition 10 can be imparted with flame retardancy by a phosphorus-based flame retardant having a specific decomposition temperature, eliminating the need to add a large amount of a flame retardant and preventing a decrease in the fluidity of the composite resin. The flame-retardant cellulose fiber composite resin composition 10 may be a fluid or solid, and may be in the form of, for example, a block, a rectangle, or a pellet for storage and distribution.

[0028] The components constituting the flame-retardant cellulose fiber composite resin composition 10 will be described below.

[0029] <Main Resin> The main resin 1 is preferably a thermoplastic resin to ensure good moldability. Examples of thermoplastic resins include olefin-based resins (including cyclic olefin-based resins), styrene-based resins, (meth)acrylic resins, organic acid vinyl ester-based resins or derivatives thereof, vinyl ether-based resins, halogen composite resins, polycarbonate-based resins, polyester-based resins, polyamide-based resins, thermoplastic polyurethane resins, polysulfone-based resins (polyethersulfone, polysulfone, etc.), polyphenylene ether-based resins (2,6-xylenol polymers, etc.), cellulose derivatives (cellulose esters, cellulose carbamates, cellulose ethers, etc.), silicone resins (polydimethylsiloxane, polymethylphenylsiloxane, etc.), rubber or elastomer (diene rubbers such as polybutadiene and polyisoprene, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylic rubbers, urethane rubbers, silicone rubbers, etc.). The above resins may be used alone or in combination. The resin is not limited to the above materials as long as it has thermoplastic properties.

[0030] Of these thermoplastic resins, the main resin 1 is preferably an olefin-based resin with a relatively low melting point. Examples of olefin-based resins include homopolymers of olefin-based monomers, copolymers of olefin-based monomers, and copolymers of olefin-based monomers with other copolymerizable monomers. Examples of olefin-based monomers include linear olefins (α-C2-20 olefins such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 4-methyl-1-pentene, and 1-octene), and cyclic olefins. These olefin-based monomers may be used alone or in combination. Of the above olefin-based monomers, linear olefins such as ethylene and propylene are preferred. Other copolymerizable monomers include, for example, fatty acid vinyl esters such as vinyl acetate and vinyl propionate; (meth)acrylic monomers such as (meth)acrylic acid, alkyl (meth)acrylates, and glycidyl (meth)acrylate; unsaturated dicarboxylic acids or anhydrides thereof such as maleic acid, fumaric acid, and maleic anhydride; vinyl esters of carboxylic acids (e.g., vinyl acetate and vinyl propionate); cyclic olefins such as norbornene and cyclopentadiene; and dienes such as butadiene and isoprene. These copolymerizable monomers may be used alone or in combination. Specific examples of olefin resins include copolymers of linear olefins (particularly α-C2-4 olefins), such as polyethylene (low-density, medium-density, high-density, or linear low-density polyethylene), polypropylene, ethylene-propylene copolymers, and terpolymers such as ethylene-propylene-butene-1.

[0031] The melt flow index (MFR) of the base resin 1 is preferably 10 g / 10 min or more, more preferably 30 g / 10 min or more, and even more preferably 50 g / 10 min or more. The higher the MFR of the resin, the higher the fluidity and the improved moldability. On the other hand, it melts more easily and drips easily during combustion tests. By combining it with cellulose, the strength increases and the viscosity of the composite resin increases, so dripping can be suppressed in the composite resin. Therefore, the MFR of the base resin 2 is preferably 10 g / min or more, more preferably 30 g / min or more, and even more preferably 50 g / min or more.

[0032] <Cellulose Fibers> Examples of the cellulose fibers 2 include cellulose fibers, lignocellulose fibers, wood flour, bamboo flour, etc. Raw materials for cellulose fibers and lignocellulose fibers include natural materials such as wood (coniferous and broad-leaved trees), cotton linters, kenaf, Manila hemp (abaca), sisal, jute, sabai grass, esparto grass, bagasse, rice straw, wheat straw, reed, and bamboo. Cellulose fibers modified with functional monomers such as acids, amines, and epoxy may also be used. Of these cellulose fibers, cellulose fibers 2 made from pulp are preferred. The cellulose fibers are not limited to pulp, as long as they are made from raw materials containing 70% by mass or more of cellulose and impurities such as lignin and hemicellulose have been removed.

[0033] The content of cellulose fiber 2 is preferably 10% by mass or more and 90% by mass or less, more preferably 30% by mass or more and 90% by mass or less, and even more preferably 50% by mass or more and 90% by mass or less, based on 100% by mass of the cellulose fiber composite resin. If the content is more than 90% by mass, the cellulose fiber content is too high, significantly reducing the fluidity of the cellulose fiber composite resin composition and making molding difficult. If the content is less than 10% by mass, the reinforcing effect of adding the cellulose fiber is reduced. Therefore, the content of the cellulose fiber is preferably 10% by mass or more and 90% by mass or less, more preferably 30% by mass or more and 90% by mass or less, and even more preferably 50% by mass or more and 90% by mass or less.

[0034] The aspect ratio of the cellulose fibers 2 is preferably 2 or more. The average fiber length of the cellulose fibers 2 is preferably 50 μm or more, and more preferably 100 μm or more. Fibers with a large aspect ratio have a strong reinforcing effect on the resin, increasing the strength of the composite resin and suppressing crumbling and dripping due to carbonization during combustion. Therefore, the aspect ratio of the cellulose fibers 2 is preferably 2 or more, and the average fiber length is preferably 50 μm or more, and more preferably 100 μm or more.

[0035] The fiber length direction of the cellulose fibers in the surface-side skin layer 11 of the cellulose fiber composite resin molding is preferably oriented at an angle of 0° to 30° relative to the surface of the composite resin molding by 50% or more, more preferably 70% or more. The skin layer 11 is formed very close to the surface that contacts the mold, for example, at a depth of about 1 mm from the outermost surface of the molding. As shown in FIG. 1 , a core layer 12 is formed deeper than the skin layer 11. Formation of a carbonized layer is effective in suppressing combustion from the surface, and if the cellulose fibers, which are the source of carbonization, are oriented parallel to the surface, the carbonized layer can be formed effectively. If the oriented angle is less than 50%, the carbonized layer cannot be formed effectively. Therefore, the fiber length direction of the cellulose fibers in the surface-side skin layer 11 of the composite resin molding is preferably oriented at an angle of 0° to 30° relative to the surface of the composite resin molding by 50% or more, more preferably 70% or more.

[0036] <Phosphorus-Based Flame Retardant> The phosphorus-based flame retardant 3 is preferably a halogen-free phosphorus-based flame retardant. Examples of phosphorus-based flame retardants include phosphate ester compounds, phosphate salts, and intumescent flame retardants. Examples of phosphate ester compounds include monomers and oligomers such as triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, and cresyl phenyl phosphate, as well as condensed phosphate ester compounds. Examples of phosphate salts include ammonium polyphosphate. Intumescent flame retardants include at least a phosphorus-based flame retardant and a nitrogen-based flame retardant. The above flame retardants may be used alone or in combination. Note that the flame retardant is not limited to the above materials as long as it contains the phosphorus element. The decomposition temperature of the phosphorus-based flame retardant can be controlled by adjusting the molecular weight of the polymer.

[0037] The phosphorus-based flame retardant 3 has a decomposition temperature T ＦＲ is the decomposition temperature T ＣｅＦ -30℃ or higher, T ＣｅＦ The temperature is preferably +30°C or lower, and the decomposition temperature T ＣｅＦ-20℃ or higher, T ＣｅＦ The decomposition temperature of each material was measured by TG / DTA, and the temperature at which the weight loss reached 5% was defined as the decomposition temperature. ＦＲ is the decomposition temperature T ＣｅＦ If the temperature is lower than −30° C., the decomposition temperature of the phosphorus-based flame retardant becomes close to the temperature during kneading and molding, and the flame retardant decomposes during the kneading and molding process, making it difficult for the phosphorus-based flame retardant to effectively exhibit its carbonization-promoting effect during the decomposition of the cellulose fiber. ＦＲ is the decomposition temperature T ＣｅＦ If the temperature is higher than +30°C, the phosphorus-based flame retardant is unlikely to effectively exhibit its carbonization promoting effect during the decomposition of cellulose fibers. ＦＲ is equal to or higher than the melting point of the base resin and the decomposition temperature T ＣｅＦ -30℃ or higher, T ＣｅＦ The temperature is preferably +30°C or lower, and the decomposition temperature T ＣｅＦ -20℃ or higher, T ＣｅＦ It is more preferable that the temperature is +20°C or lower.

[0038] Furthermore, the phosphorus-based flame retardant 3 has a decomposition temperature T ＣｅＦ -30℃ or higher, T ＣｅＦ Decomposition temperature T below +30°C ＲＦ１ and the decomposition temperature T ｐ -30℃ or higher, T ｐ Decomposition temperature T below +30°C ＲＦ２ and a second phosphorus-based flame retardant 32 having a decomposition temperature T ＣｅＦ -20℃ or higher, T ＣｅＦ Decomposition temperature T below +20°C ＲＦ１ and the decomposition temperature T ｐ -20℃ or higher, T ｐ It is more preferable that the flame retardant 31 is made up of at least two kinds of phosphorus-based flame retardants, and the second phosphorus-based flame retardant 32 has a decomposition temperature T ＦＲ is the decomposition temperature TＣｅＦ If the temperature is lower than −30° C., the decomposition temperature of the first phosphorus-based flame retardant becomes close to the temperature during kneading and molding, and the flame retardant decomposes during the kneading and molding processes, making it difficult for the first phosphorus-based flame retardant to effectively exhibit its carbonization-promoting effect during the decomposition of the cellulose fiber. ＦＲ１ is the decomposition temperature T ＣｅＦ If the decomposition temperature T is higher than +30° C., the carbonization promoting effect of the phosphorus-based flame retardant is not effectively exhibited during the decomposition of the cellulose fiber. ＦＲ２ is the decomposition temperature T ｐ Below -30°C or T ｐ If the temperature is higher than +30°C, the carbonization promoting effect of the second phosphorus-based flame retardant is difficult to exhibit effectively when the base resin decomposes. ＣｅＦ -30℃ or higher, T ＣｅＦ When only the (first) phosphorus-based flame retardant 31 having a decomposition temperature of +30° C. or less is used, the promotion of carbonization of the main resin is difficult to function effectively. ＣｅＦ -30℃ or higher, T ＣｅＦ Decomposition temperature T below +30°C ＲＦ１ and the decomposition temperature T ｐ -30℃ or higher, T ｐ It is preferable that the flame retardant is composed of at least two kinds of materials, a first phosphorus-based flame retardant 32 having a decomposition temperature of +30° C. or less, and a second phosphorus-based flame retardant 33 having a decomposition temperature of +30° C. or less. ＣｅＦ -20℃ or higher, T ＣｅＦ The first phosphorus-based flame retardant 31 has a decomposition temperature of +20° C. or less, and the decomposition temperature T ｐ -20℃ or moreT ｐ It is more preferable that the flame retardant 32 be composed of at least two types of second phosphorus-based flame retardants 32 having a decomposition temperature of +20° C. or less.

[0039] The phosphorus-based flame retardant 3 is preferably 1% by mass or more and 30% by mass or less, and more preferably 5% by mass or more and 20% by mass or less, relative to 100% by mass of the total amount of the base resin, cellulose fiber, and phosphorus-based flame retardant. If the phosphorus-based flame retardant is less than 1% by mass, the amount of flame retardant is too small, making it difficult to impart flame retardancy to the composite resin composition (molded product). If the phosphorus-based flame retardant is more than 30% by mass, the amount of phosphorus-based flame retardant is too large, resulting in a decrease in the fluidity of the composite resin. Therefore, the phosphorus-based flame retardant is preferably 1% by mass or more and 30% by mass or less, and more preferably 5% by mass or more and 20% by mass or less, relative to 100% by mass of the total amount of the base resin, cellulose fiber, and phosphorus-based flame retardant.

[0040] The phosphorus-based flame retardant 3 has a phosphorus content in the phosphorus compound of 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more, based on a total of 100% by mass of the base resin, cellulose fiber, and phosphorus-based flame retardant. The phosphorus content is calculated from the ratio of the atomic weight of phosphorus contained to the molecular weight of the compound. If the phosphorus content is less than 5% by mass, the phosphorus content is low, resulting in a low flame retardant effect per weight. In this case, it is necessary to increase the amount of flame retardant added. Therefore, the phosphorus-based flame retardant 3 has a phosphorus content in the phosphorus compound of 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more.

[0041] <Acid-Modified Polyolefin> The acid-modified polyolefin 4 may have an acid-modified structure in the molecule, and specific examples include maleic anhydride-modified polyolefins. Acid-modified polyolefins include graft copolymers and alternating copolymers, with alternating copolymers being preferred. The carbonization-promoting effect of phosphorus-based flame retardants and the like is due to dehydration in the molecule, so resins containing oxygen elements in the molecule effectively promote carbonization. Since graft copolymers have an acid-modified structure in the side chain, carbonization promotion in the side chain proceeds, but the effect on promoting carbonization of the main chain is thought to be not that great. On the other hand, since alternating copolymers have an acid-modified structure in the main chain, carbonization promotion in the main chain proceeds effectively. Therefore, alternating copolymers are preferred as modified polyolefins.

[0042] In the acid-modified polyolefin 4, the mass ratio of the base resin to the acid-modified polyolefin is preferably 100:10 or more, and more preferably 100:20 or more. If the mass ratio of the base resin to the acid-modified polyolefin is less than 100:10, the proportion of the acid-modified polyolefin is low, and the carbonization-promoting effect of the composite resin is small. Therefore, the mass ratio of the base resin to the acid-modified polyolefin is preferably 100:10 or more, and more preferably 100:20 or more.

[0043] <Additives> The flame-retardant cellulose fiber composite resin composition may contain various additives in addition to the various materials described above. For example, when producing the flame-retardant cellulose fiber composite resin composition, in addition to polypropylene (main resin), pulverized pulp (cellulose fiber), and a phosphorus-based flame retardant, a dispersant, a plasticizer, an antioxidant, a stabilizer, a colorant, etc. may be added.

[0044] <Method for producing flame-retardant cellulose fiber composite resin composition> The method for producing a flame-retardant cellulose fiber composite resin composition includes a step (kneading step) of kneading a base resin, cellulose fibers, and a phosphorus-based flame retardant to form a flame-retardant cellulose fiber composite resin composition. Furthermore, the method for producing a cellulose fiber composite resin composition may include a mixing step for adhering the phosphorus-based flame retardant to the cellulose fibers. By adhering the phosphorus-based flame retardant to the surface of the cellulose fibers before the kneading step, carbonization of the cellulose fibers during combustion can be promoted. Furthermore, the presence of the phosphorus-based flame retardant on the surface of the cellulose fibers reduces direct contact between the cellulose fibers, thereby suppressing aggregation of the cellulose fibers.

[0045] Examples of kneading devices used in the kneading step of the method for producing a flame-retardant cellulose fiber composite resin composition include single-screw kneaders, twin-screw kneaders, roll kneaders, kneaders, Banbury mixers, and combinations thereof. Continuous twin-screw kneaders and continuous roll kneaders are preferred because they are easy to apply high shear and are suitable for mass production. Other kneading methods may also be used as long as they can apply high shear stress. Furthermore, because cellulose fibers are prone to thermal degradation, it is preferable to knead them at as low a temperature as possible.

[0046] <Flame-retardant cellulose fiber composite resin molding> The cellulose fiber composite resin molding according to the first embodiment is a cellulose fiber composite resin molding made of a cellulose fiber composite resin composition containing a base resin, cellulose fibers, and a phosphorus-based flame retardant.

[0047] <Method for Producing Flame-Retardant Cellulose Fiber Composite Resin Molded Article> A method for producing a flame-retardant cellulose fiber composite resin molded article according to the first embodiment is, for example, as follows. (1) First, a base resin, cellulose fiber, and a phosphorus-based flame retardant are kneaded to obtain a flame-retardant cellulose fiber composite resin composition (kneading step). This kneading step is substantially the same as the kneading step in the method for producing a flame-retardant cellulose fiber composite resin composition. Examples of kneading devices used in the kneading step include single-screw kneaders, twin-screw kneaders, roll kneaders, kneaders, Banbury mixers, and combinations thereof. Continuous twin-screw kneaders and continuous roll kneaders are preferred from the viewpoints of easy application of high shear and high mass productivity. Other kneading methods that can apply high shear stress are also acceptable. Furthermore, because cellulose fibers are prone to thermal degradation, it is preferable to knead them at as low a temperature as possible.

[0048] The composite resin composition extruded from the kneading device is cut using a pelletizer or the like to produce, for example, pellets. Pelletization methods include, for example, in-air hot cutting, underwater hot cutting, and strand cutting, which are performed immediately after the resin is melted. Alternatively, there is also a crushing method in which a molded body or sheet is molded and then crushed and cut.

[0049] (2) Next, the obtained cellulose fiber composite resin composition is molded to obtain a molded article. The molded article is produced by molding the pellets. Molding methods include injection molding, extrusion molding, compression molding, and blow molding. In this manner, a flame-retardant cellulose fiber composite resin molded article is obtained.

[0050] Hereinafter, each example and each comparative example carried out by the inventors will be described.

[0051] (Examples 1 to 5, Comparative Examples 1 to 3) FIG. 2 is a diagram showing the conditions and measurement results for Examples 1 to 5 and Comparative Examples 1 to 3.

[0052] The flame-retardant cellulose fiber composite resin composition and the flame-retardant cellulose fiber composite resin molding were produced by the following manufacturing method. As described above, a single-screw kneader, a twin-screw kneader, a roll kneader, a kneader, a Banbury mixer, or a combination thereof can be used as the kneading device. In the examples, a twin-screw kneader was used.

[0053] Polypropylene (manufactured by Japan Polypropylene Corporation, product name: BC03C) was used as the base resin, ground pulp as the cellulose fiber, ADK STAB FP-2500S (manufactured by ADEKA) as the phosphorus-based flame retardant, and maleic anhydride-modified polypropylene (manufactured by Sanyo Chemical Industries, Ltd., product name: UMEX) as the dispersant, all weighed out to a mass ratio of 24:55:20:1. Mixtures of the base resin and dispersant, and ground pulp and phosphorus-based flame retardant were separately fed into the kneader. Hardwood pulp (manufactured by Mitsubishi Paper Mills, product name: Mitsubishi Kitakami LBKP) was used as the starting material for ground pulp. This pulp was ground in a grinder to obtain ground pulp. The size of the cellulose fibers was adjusted during the grinding process. As for the grinding method, dry grinding is preferred because wet grinding requires a drying process after grinding and causes aggregation during drying.

[0054] The mixture was melted, kneaded, and dispersed in a twin-screw kneader (KRC Kneader manufactured by Kurimoto Iron Works Co., Ltd.). The shear force can be changed by changing the screw configuration of the twin-screw kneader, and a low-shear type was used in Example 1. The cellulose fiber composite resin composition discharged from the twin-screw kneader was hot-cut to produce cellulose fiber composite resin pellets made of the cellulose fiber composite resin composition.

[0055] The cellulose fiber composite resin pellets were used to prepare test pieces of composite resin moldings using an injection molding machine (180AD manufactured by Japan Steel Works, Ltd.). The shape of the test pieces was changed depending on the evaluation items described below, and Type A1 dumbbell-shaped test pieces were prepared for elastic modulus measurements. The molding conditions for the dumbbell-shaped test pieces were a resin temperature of 200°C, a mold temperature of 40°C, an injection speed of 60 mm / s, and a holding pressure of 100 MPa. The pellets were fed into the screw of the molding machine via a hopper, and the penetration rate during this process was measured as the amount of pellet loss per hour, which was confirmed to be constant.

[0056] [Evaluation items for composite resin composition and molded article] (Flame retardancy of composite resin) The obtained cellulose composite resin pellets were used to evaluate the flame retardancy by a flammability test using an MCC (microcalorimeter). The specific heat release and combustion residue rate were used as indicators of flame retardancy. The specific heat release of the pellets was 376 J / g·K, and the combustion residue rate was 26.6%.

[0057] (Fluidity of Composite Resin) Using the obtained cellulose composite resin pellets, MFR (melt flow rate) was measured to evaluate fluidity based on JIS K7210-1:2014 (ISO1133-1:2011). The MFR of the pellets was 1.8 g / 10 min.

[0058] (Strength of Composite Resin Molded Product) A three-point bending test was carried out using the obtained Type A1 dumbbell tester. The modulus of elasticity of the test piece was 48 MPa.

[0059] (Fiber orientation in the skin layer) A portion was cut out from the obtained No. 1 dumbbell-shaped test piece, and a polarizing microscope measurement of the cross section was performed. On the obtained polarizing microscope measurement image, the angle of the fiber length direction of the cellulose fibers in the skin layer was measured, with the surface of the test piece set at 0°. The ratio of cellulose fibers in the test piece with an angle of 0° or more and 30° or less was 72%.

[0060] In Example 2, the amount of flame retardant added was reduced compared to Example 1, and the mass ratio of base resin: pulp: phosphorus-based flame retardant: dispersant was changed to 38:55:5:2. Other conditions were the same as in Example 1, and cellulose fiber composite resin pellets and a molded product were produced. Evaluations similar to those in Example 1 were also carried out.

[0061] (Example 3) In Example 3, two types of phosphorus-based flame retardants (phosphorus-based flame retardant 31: Adeka STAB FP-2500S (manufactured by ADEKA), and phosphorus-based flame retardant 32: Adeka STAB FP-2100JC (manufactured by ADEKA)) were used. The other material conditions and process conditions were the same as in Example 1, and cellulose fiber composite resin pellets and molded articles were produced. Evaluations similar to those in Example 1 were also carried out.

[0062] In Example 4, the amount of flame retardant added was reduced compared to Example 1, the mass ratio of base resin: pulp: phosphorus-based flame retardant: dispersant was changed to 38:55:5:2, and cellulose fibers with long fiber length were used. The other material conditions and process conditions were the same as in Example 1, and cellulose fiber composite resin pellets and molded articles were produced. The same evaluations as in Example 1 were also carried out.

[0063] In Example 5, EXOLIT AP422 (manufactured by Clariant), a phosphate, was used as the phosphorus-based flame retardant. Cellulose fiber composite resin pellets and a molded product were produced under the same material and process conditions as in Example 1. Evaluations similar to those in Example 1 were also carried out.

[0064] Comparative Example 1 In Comparative Example 1, no phosphorus-based flame retardant was added, and the mass ratio of base resin: pulp: phosphorus-based flame retardant: dispersant was changed to 43:55:0:2. Other material conditions and process conditions were the same as in Example 1, and composite resin pellets and molded bodies were produced. Evaluations similar to those in Example 1 were also carried out.

[0065] In Comparative Example 2, magnesium hydroxide was used as the flame retardant instead of the phosphorus-based flame retardant. Other material conditions and process conditions were the same as in Example 1, and composite resin pellets and molded articles were produced. Evaluations similar to those in Example 1 were also carried out.

[0066] Comparative Example 3 In Comparative Example 3, the decomposition temperature T ＣｅＦ A phosphorus-based flame retardant (MPP-A manufactured by Sanwa Chemical) with a decomposition temperature exceeding +30°C was used. Other material and process conditions were the same as in Example 1, and composite resin pellets and molded articles were produced. Evaluations similar to those in Example 1 were also carried out.

[0067] The measurement results for each of Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1 in FIG.

[0068] In Example 2, in which a dispersant was used, the amount of flame retardant was less than that in Example 1, and therefore the flame retardancy was reduced.

[0069] In Example 3, in which two types of phosphorus-based flame retardants were used, effective flame retardants were used for both the base resin and the cellulose fibers, and therefore the flame retardancy was improved compared to Example 1.

[0070] In Example 4, in which cellulose fibers having a large fiber length were used, the fluidity was lower than that of Example 2, but the flame retardancy was slightly improved.

[0071] In Example 5, in which phosphate was used as the phosphorus-based flame retardant, the flame retardancy was slightly lower than that of Example 1.

[0072] In Comparative Example 1, in which no flame retardant was used, the absence of a flame retardant prevented the promotion of carbonization, resulting in a decrease in flame retardancy.

[0073] In Comparative Example 2, in which magnesium hydroxide was used as the flame retardant, the flame retardant effect of magnesium hydroxide is mainly endothermic, so carbonization of the composite resin was not promoted, and the flame retardancy was lower than that of a phosphorus-based flame retardant.

[0074] The decomposition temperature T of cellulose fiber in flame retardant ＣｅＦ In contrast, T ＣｅＦIn Comparative Example 3, which used a phosphorus-based flame retardant with a decomposition temperature of +30°C or higher, the effect of the flame retardant was reduced due to the difference between the decomposition temperature of the cellulose fiber and the decomposition temperature of the phosphorus-based flame retardant, resulting in lower flame retardancy than in Example 1.

[0075] From the above evaluation, the decomposition temperature T ＣｅＦ -30℃ or moreT ＣｅＦ When a phosphorus-based flame retardant having a decomposition temperature of +30° C. or less was not added, carbonization of the cellulose and the base resin was not promoted, and sufficient flame retardancy could not be obtained.

[0076] As described above, the cellulose fiber composite resin composition according to the present disclosure can be made flame retardant while maintaining moldability by containing a main resin, cellulose fibers, and a phosphorus-based flame retardant having a specific decomposition temperature.

[0077] The flame-retardant cellulose fiber composite resin composition according to the present disclosure has high flame retardancy, high fluidity, and high moldability. Flame-retardant cellulose fiber composite resin molded articles obtained by using the flame-retardant cellulose fiber composite resin composition according to the present disclosure can be used for applications requiring flame retardancy, such as housings for home appliances, building materials, and exterior parts for automobiles.

[0078] REFERENCE SIGNS LIST 1 Base resin 2 Cellulose fiber 3 Phosphorus-based flame retardant 4 Acid-modified polyolefin 10 Cellulose fiber composite resin composition (molded body)

Claims

1. A flame retardant film comprising a base resin, cellulose fibers, and a phosphorus-based flame retardant, the decomposition temperature T ＦＲ is the decomposition temperature T of the cellulose fiber ＣｅＦ About T ＣｅＦ -30℃ or higher, T ＣｅＦ A flame-retardant cellulose fiber composite resin composition having a flame resistance of +30°C or less.

2. The phosphorus-based flame retardant has a decomposition temperature T ＣｅＦ About T ＣｅＦ -30℃ or moreT ＣｅＦ Decomposition temperature T below +30°C ＲＦ１ and a first phosphorus-based flame retardant having a decomposition temperature T ｐ About T ｐ -30℃ or higher, T ｐ Decomposition temperature T below +30°C ＲＦ２ The flame-retardant cellulose fiber composite resin composition according to claim 1, comprising two types of flame retardants: a phosphorus-based flame retardant having a formula (I) and a second phosphorus-based flame retardant having a formula (II).

3. A flame-retardant cellulose fiber composite resin composition according to claim 1 or 2, wherein the phosphorus-based flame retardant has a phosphorus content of 5 mass% or more in the phosphorus compound.

4. A flame-retardant cellulose fiber composite resin composition according to claim 1 or 2, wherein the amount of cellulose fiber added is 10% by mass or more and 90% by mass or less.

5. A flame-retardant cellulose fiber composite resin composition according to claim 1 or 2, wherein the amount of the phosphorus-based flame retardant added is 1% by mass or more and 30% by mass or less.

6. A flame-retardant cellulose fiber composite resin composition according to claim 1 or 2, wherein the melt flow index (MFR) of the base resin is 10 g / min or more.

7. A flame-retardant cellulose fiber composite resin composition according to claim 1 or 2, wherein the main resin is a polyolefin.

8. A flame-retardant cellulose fiber composite resin composition according to claim 1 or 2, further comprising an acid-modified polyolefin, the mass ratio of the base resin to the acid-modified polyolefin being 100:10 or more.

9. A flame-retardant cellulose fiber composite resin composition according to claim 1 or 2, wherein the cellulose fibers have an aspect ratio of 2 or more and an average fiber length of 50 μm or more.

10. A flame-retardant cellulose fiber composite resin composition according to claim 1 or 2, wherein the cellulose fibers have the phosphorus-based flame retardant attached to their surfaces.

11. A cellulose fiber composite resin molding comprising a base resin, cellulose fiber, and a phosphorus-based flame retardant, wherein the decomposition temperature T ＦＲ is the decomposition temperature T of the cellulose fiber ＣｅＦ About T ＣｅＦ -30℃ or higher, T ＣｅＦ A flame-retardant cellulose fiber composite resin molding having a temperature of +30°C or lower.

12. A flame-retardant cellulose fiber composite resin molding as described in claim 11, wherein the fiber length direction of the cellulose fibers in the skin layer on the surface side of the flame-retardant cellulose fiber composite resin molding is oriented at an angle of 0° or more and 30° or less relative to the surface of the flame-retardant cellulose fiber composite resin molding by 50% or more.

13. A method for producing a flame-retardant cellulose fiber composite resin molded body, comprising: a mixing step for adhering the phosphorus-based flame retardant to the cellulose fibers; a kneading step for kneading a base resin, cellulose fibers, and the phosphorus-based flame retardant to obtain a cellulose fiber composite resin composition; and a molding step for molding the cellulose fiber composite resin composition to obtain a cellulose fiber composite resin molded body.

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