JP2007098583A - Manufacturing method of woody fiber molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a woody fiber molded product constituted so that woody fibers are bonded by a polylactic acid type aliphatic polyester and superior in strength and moisture resistance. <P>SOLUTION: The manufacturing method of the woody fiber molded product includes a mat body manufacturing method for manufacturing a mat body by mixing woody fibers and polylactic acid type aliphatic polyester fibers, a preforming material manufacturing process for manufacturing a preforming material by applying a compatible copolymer to the mat body and a molding process for pressing the preforming material at a temperature bringing the polylactic acid type aliphatic polyester fibers to a softened or molten state to mold the same. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for producing a wood fiber molded product in which wood fibers are bonded with a polylactic acid aliphatic polyester.

With the recent improvement in environmental conservation awareness, not only the functionality at the time of use but also the reduction of the environmental load at the time of disposal and the ease of disposal are required when designing various products.
Conventionally, a wood-based fiber molded body used as a member of a vehicle, a building, furniture, or the like has been used in which a wood-based fiber is bonded with a binder such as a phenol resin or a polyolefin resin. However, wood fibers, which are natural materials, are biodegradable. However, binder resins such as phenol resins and polyolefin resins are hardly degradable. It was not enough. Therefore, an attempt has been made to use a biodegradable resin such as a polylactic acid resin instead of these hardly decomposable binder resins. For example, Patent Document 1 discloses water of polylactic acid resin as a binder for kenaf fibers. A method is disclosed in which a dispersion is applied and the obtained pre-molding material is heated and compressed to obtain a molded body. By using a biodegradable resin such as polylactic acid as the binder resin, the biodegradability of the wood-based fiber molded body is significantly improved and can be decomposed by landfill or composting (composting). The environmental load can be reduced.

JP 2003-55871 A

However, since biodegradable resins are decomposed by the action of microorganisms in the soil, they have the advantage of having a low environmental impact during disposal, while they are gradually hydrolyzed by moisture in the air even during use. Therefore, there is a disadvantage that the strength decreases and deteriorates with time. In particular, in a molded body in which wood fibers are bonded with a biodegradable resin, the moisture of the wood fibers is high, so the moisture absorbed by the wood fibers promotes the hydrolysis of the biodegradable resin, and the wood There has also been a concern about the problem that the bonding strength between the base fibers decreases and the strength of the molded body itself decreases.
Therefore, the present invention relates to the production of a molded product in which wood fibers are bonded with polylactic acid aliphatic polyester, and is a wood fiber molded product that can obtain a wood fiber molded product having high strength and excellent moisture resistance. An object is to provide a manufacturing method.

A first invention for solving the problem is a method for producing a wood-based fiber molded body, in which a mat body is produced by mixing wood-based fibers and polylactic acid aliphatic polyester fibers to create a mat body, A pre-molding material creation step of creating a pre-molding material by applying a compatible copolymer to the mat body, and heating the pre-molding material at a temperature at which the polylactic acid-based aliphatic polyester fiber is in a softened or molten state And a forming step of forming the shape into a predetermined shape by pressurization, and a method for producing a wood-based fiber molded body.
According to the first invention, a pre-molding material is prepared by applying a compatible copolymer that is compatible with both the wood fiber and the polylactic acid aliphatic polyester to the mat body. By pressing the pre-molding material with heating at a temperature at which the aromatic polyester is in a softened state or molten state, the compatible copolymer becomes compatible with both the wood fiber and the polylactic acid aliphatic polyester. Bonding is stronger, and the bond strength between the wood fiber and the polylactic acid aliphatic polyester can be favorably increased. As a result, it is possible to obtain a wood-based fiber molded body in which the wood-based fibers are uniformly and strongly bonded, high in strength, and excellent in moisture resistance.
In addition, according to the first invention, in order to provide a compatible copolymer after forming a mat body composed of wood-based fibers and polylactic acid-based aliphatic polyester fibers, the compatible copolymer is added to the mat body. Can be uniformly penetrated into the inside. Therefore, the compatible copolymer can be satisfactorily brought into contact with the wood fiber and the polylactic acid aliphatic polyester fiber. As a result, it is possible to obtain a wood-based fiber molded body in which the wood-based fibers are uniformly and strongly bonded, high in strength, and excellent in moisture resistance.

A second invention is a method for producing a wood-based fiber molded body according to the first invention, wherein the preforming material is preformed between the pre-molding material preparation step and the molding step. It is a manufacturing method of the wood type fiber molded object characterized by including a process.
According to the second invention, for example, by compressing the pre-molding material and pre-molding it into a shape with a small volume, the pre-molding material can be easily transported and handled during storage, and a large amount of pre-molding can be done in a smaller space Materials can be transported and stored. Therefore, since the preform can be stored in consideration of convenience such as production efficiency, a wood-based fiber molded body having high strength and excellent moisture resistance can be produced more efficiently.

A third invention is a method for producing a wood-based fiber molded body according to the first invention or the second invention, wherein the compatible copolymer comprises the first polymerizable monomer and the second A copolymer obtained by polymerizing the polymerizable monomer, wherein the first polymerizable monomer has a polymerizable double bond portion and a hydrophilic group, and the second polymerizable monomer The body has a polymerizable double bond portion and an epoxy group, and is a method for producing a wood-based fiber molded body.
According to the third invention, the compatible copolymer is compatible with the wood fiber due to the hydrophilic group derived from the first polymerizable monomer, and the epoxy copolymer derived from the second polymerizable monomer. Fits with lactic acid aliphatic polyester. Therefore, by being heated in the molding process, the compatible copolymer binds well to both the wood fiber and the lactic acid aliphatic polyester, and the bond strength between the wood fiber and the polylactic acid aliphatic polyester is increased. Improve. At the same time, the compatible copolymer binds to the polylactic acid aliphatic polyester, thereby increasing the molecular weight of the polylactic acid aliphatic polyester or forming a three-dimensional structure. Therefore, the strength of the molded body is improved, and the bonding strength between the wood fibers can be favorably increased. As a result, a wood-based fiber molded body having high strength and excellent moisture resistance can be obtained.

A fourth invention is a method for producing a wood fiber molded product according to the third invention, wherein the first polymerizable monomer has a polyalkylene oxide chain as a hydrophilic group. It is a manufacturing method of a body.
According to the fourth invention, the first polymerizable monomer has a strong affinity for the wood fiber due to the hydrophilic group, and as a result, a wood fiber molded product having high strength and excellent moisture resistance can be obtained. .

A fifth invention is a method for producing a wood-based fiber molded body according to the third invention or the fourth invention, wherein the first polymerizable monomer is methoxypolyethylene glycol mono (meth) acrylate. The method for producing a wood-based fiber molded body in which the second polymerizable monomer is glycidyl (meth) acrylate.
According to the fifth invention, by using a polymerizable monomer having a good affinity for both the wood fiber and the polylactic acid aliphatic polyester, the bond strength between the wood fiber and the polylactic acid aliphatic polyester is increased. Can be improved. As a result, it is possible to obtain a wood fiber molded body having higher strength and excellent moisture resistance.

According to a sixth aspect of the present invention, in the method for producing a wood-based fiber molded body according to any one of the first to fifth aspects of the invention, in the pre-molding material creation step, the mat body is compatible with the compatible co-polymer. This is a method for producing a wood-based fiber molded body in which coalescence is applied in the form of an aqueous solution.
According to the sixth invention, in the molding step, moisture is evaporated by heating and pressurizing the wood-based fiber containing moisture, and crystallization of cellulose which is the main component of the wood-based fiber proceeds, While improving an intensity | strength, it can make it difficult to absorb a water | moisture content. As a result, it is possible to obtain a wood fiber molded body having higher strength and more excellent moisture resistance.

7th invention is a manufacturing method of the wood type fiber molded object in any one of the said 1st invention thru | or 6th invention, The said wood type fiber is a fiber derived from kenaf. Is the method.
Kenaf-derived fibers are characterized by high cellulose content, long fibers and high strength. Therefore, according to the seventh aspect of the present invention, a wood fiber molded product having higher strength and excellent moisture resistance can be obtained.

An eighth invention is a method for producing a woody fiber molded body according to any one of the first to seventh inventions, wherein the polylactic acid-based aliphatic polyester fiber is a fiber made of polylactic acid. It is a manufacturing method of a wood type fiber molding.
Polylactic acid is an environmentally friendly material because lactic acid, which is a raw material, can be collected from a plant and the plant absorbs carbon dioxide that causes global warming. Therefore, according to the eighth invention, it is possible to obtain a wood-based fiber molded body having not only high strength and excellent moisture resistance but also less burden on the global environment.

  According to the present invention, a method for producing a wood-based fiber molded body capable of obtaining a molded body having high strength and excellent moisture resistance, relating to the production of a molded body in which wood-based fibers are bonded with a polylactic acid-based aliphatic polyester. Can be provided.

  The wood-based fiber molded body produced by the present invention is a molded body in which wood-based fibers are bonded with a polylactic acid-based aliphatic polyester. Examples of this molded body include, for example, a single layer or a plurality of layers of wood A board material (plate-like member) of the system can be mentioned. This board material may be a board material that is subjected to bending molding or drawing molding as necessary. Although not limited, the wood-based fiber molded body produced by the present invention is a member of an interior surface of a vehicle, a building, a ship, etc., such as an interior wall material, a floor material, a ceiling material, and furniture. It can be applied to surface material. As a vehicle member, for example, it can be applied to a door trim, an instrument panel, a pillar cover, and the like.

  As shown in FIG. 1, the method for producing a wood-based fiber molded body according to the present invention includes a mat body preparation step of forming a mat body by mixing wood-based fibers and polylactic acid aliphatic polyester fibers, and the mat. A pre-molding material preparation step in which a compatible copolymer is applied to the body to prepare a pre-molding material; And a molding step of molding into a predetermined shape by pressing. In the production method of the present invention, in order to provide a compatible copolymer after forming a mat body from wood fibers and polylactic acid aliphatic polyester fibers, a compatible copolymer is provided inside the mat body. It can be fully penetrated. As a result, it is possible to produce a wood fiber molded body having high bonding strength between wood fibers and excellent moisture resistance.

The main materials used in the production method according to the present invention will be described in order below.
Wood fiber is a fiber material that can be extracted from a wood material. This wood fiber can be obtained by, for example, defibrating a wood material such as woods and vegetation. Specific examples of the woody material include kenaf, sisal, jute, ramie, bagasse and the like. In particular, the wood fiber obtained from kenaf bast has a high content of cellulose, which is a fiber skeleton and a main component, and is a long fiber and high strength. Accordingly, if a kenaf bast fiber is used, a wood-based fiber molded body having high strength can be obtained. Kenaf is a one-year plant that grows quickly, can be cultivated in a short period of time, and has a high carbon dioxide absorption capacity. Therefore, it is an extremely suitable woody material from the viewpoint of environmental conservation.

  Polylactic acid-based aliphatic polyesters include, for example, polymers of oxyacids such as lactic acid, malic acid, and glucose acid or copolymers thereof, dibasic acid polyesters such as polybutylene succinate, polyethylene succinate, and polybutylene adipate. Can be mentioned. In particular, polycarboxylic acids such as polylactic acid, copolymers of polylactic acid and other hydroxycarboxylic acids, polycaprolactone, copolymers of caprolactone and other hydroxycarboxylic acids, poly-3-hydroxybutyric acid esters, etc. Preferred are aliphatic aliphatic polyesters. Furthermore, polylactic acid obtained by polymerizing lactic acid is more preferable because lactic acid as a raw material can be obtained by decomposing starch collected from plants such as corn and sweet potato.

The compatible copolymer is a polymer that is compatible with both wood fibers and polylactic acid aliphatic polyesters.
Originally, wood fiber has a large polarity, ie, a hydrophilic surface, in which cellulose as a main component has many hydroxyl groups. For this reason, the wood fiber is compatible with a material having a hydrophilic surface having a large polarity. On the other hand, polylactic acid aliphatic polyester is a polymer mainly composed of an alkyl chain and an alkoxycarbonyl chain, and has a high lipophilicity. For this reason, compatibility with a wood fiber having a large polarity, that is, familiarity is not good, and compatibility with a material having a surface with a smaller polarity is good.

  Therefore, the compatible copolymer is composed of a polymer having both a hydrophilic portion that is compatible with the wood fiber and a lipophilic portion that is compatible with the polylactic acid aliphatic polyester. The compatible copolymer is preferably a polymer having a hydrophilic part and a lipophilic part in a dispersed state in a polymer chain, and between the wood fiber and the polylactic acid aliphatic polyester, Bonding is stronger and the bond strength between the wood fiber and the polylactic acid aliphatic polyester can be increased favorably. Such a compatible copolymer is typically a polymer having both a hydrophilic group and a lipophilic group as side chains, and has a polymerizable double bond and a first polymerizable monomer having a hydrophilic group. It is obtained by polymerizing a raw material containing a monomer and a second polymerizable monomer having a polymerizable double bond and having a lipophilic group.

  The first polymerizable monomer has a polymerizable double bond portion and a hydrophilic group. Typical examples of the polymerizable double bond include a vinyl group, an allyl group, an acryloyl group, and a methacryloyl group. The hydrophilic group is not limited, and examples thereof include a hydroxyl group, an alkylene oxide chain, a quaternary ammonium group, a sulfonic acid group, or a salt thereof. Specific examples of the first polymerizable monomer include allyl alcohol, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, glycerol di (meth) acrylate, polyethylene glycol mono (meth) acrylate, and methoxypolyethylene. Glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol polypropylene glycol mono (meth) acrylate, 2-sulfoethyl (meth) acrylate, (meth) acryloyloxytrimethylammonium chloride, (meth) acryloyloxyhydroxypropyltrimethyl Ammonium chloride, (meth) acryloyloxytriethylammonium chloride, (meth) acryloyloxytrimethyl There are ammonium methyl sulfate, trimethyl-3-methacrylamidopropylammonium chloride, vinyl sulfonic acid sodium salt, allyl sulfonic acid ammonium salt, and methallyl sulfonic acid triethylamine salt. Of these, one or a combination of two or more may be used. it can. The hydrophilic group in the first polymerizable monomer is preferably a hydrophilic group that does not contain active hydrogen or hardly generates active hydrogen. For example, an alkoxypolyalkylene oxide group is preferable, and specifically, a methoxypolyethylene oxide group is preferable. As a specific polymerizable monomer, methoxypolyethylene glycol mono (meth) acrylate is preferable.

  The second polymerizable monomer has a polymerizable double bond portion and a lipophilic group. In particular, the lipophilic group is preferably an epoxy group because the compatibility with the polylactic acid aliphatic polyester is very good. It also has activity for the binding reaction with polylactic acid aliphatic polyester at the softening temperature (including melting temperature or higher) of polylactic acid aliphatic polyester. It is more preferable for improving durability. The polymerizable double bond portion of the second polymerizable monomer is typically a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, or the like, like the first polymerizable monomer. Acrylic acid esters or methacrylic acid esters can be used. The second polymerizable monomer has an epoxy group, and glycidyl (meth) acrylate is typically preferable.

  The mixing ratio of the first polymerizable monomer and the second polymerizable monomer in the compatible copolymer is not particularly limited. For this reason, for example, the ratio of the 1st polymerizable monomer and the 2nd polymerizable monomer can be made into a desired ratio by the weight ratio of 1: 9-9: 1. Preferably, it is prepared so that the familiarity with the wood fiber and the familiarity with the polylactic acid-based aliphatic polyester are the same. Therefore, typically, the weight ratio of the first polymerizable monomer to the second polymerizable monomer is 1: 1, which is familiar with the wood fiber and the polylactic acid aliphatic polyester. This is preferable because it is more uniform and exhibits a good bonding force.

Of course, the compatible copolymer may be prepared by polymerizing other polymerizable monomers together with the first and second polymerizable monomers. For example, (meth) acrylic acid having a linear alkoxylate such as lauryl acrylate may be included. By including other polymerizable monomers, for example, the stereoregularity of the compatible copolymer can be controlled.
The compatible copolymer can use a known polymerization method of a monomer having a polymerizable double bond, and can be prepared by a radical polymerization reaction or an addition polymerization reaction, and thus detailed description thereof is omitted.
Although the molecular weight of a compatible copolymer is not specifically limited, 5000 or more and 100000 or less are preferable, More preferably, it is 10000-30000. When the molecular weight is less than 5,000, it tends to bleed and poor appearance after molding. Moreover, when molecular weight exceeds 100,000, the effect | action of compatibilization falls and a bending physical property tends to fall. In addition, a compatible copolymer having a molecular weight of 10,000 to 30,000 is more preferable because it is difficult to bleed and has good compatibility.

  The compatible copolymer is compatible with both wood fiber and polylactic acid aliphatic polyester, and not only improves the bond strength, but also when heated in contact with the polylactic acid aliphatic polyester, the polylactic acid aliphatic polyester To increase the molecular weight of the polylactic acid aliphatic polyester or to form a three-dimensional structure. Therefore, by causing the compatible copolymer to act appropriately, the strength of the polylactic acid-based aliphatic polyester can be improved, hydrolysis can be made difficult, and moisture resistance can be improved.

  In the present invention, the polylactic acid-based aliphatic polyester is used by being fiberized by a known spinning method such as melting by heating, extruding into air from pores, and cooling and solidifying. In the present specification, the fiberized polylactic acid-based aliphatic polyester is referred to as “polylactic acid-based aliphatic polyester fiber”. The polylactic acid-based aliphatic polyester fiber can be used by crimping or cutting as appropriate. The polylactic acid-based aliphatic polyester resin can be used by mixing one kind or several kinds of resins. Moreover, auxiliary materials, such as a plasticizer, can also be added and used as needed.

  Below, each process contained in the manufacturing method of the wood type fiber molded object which concerns on this invention is demonstrated. As shown in the flowchart of FIG. 1, the method for producing a wood-based fiber molded body according to the present invention includes a “mat body creating process”, a “pre-molding material creating process”, a “molding process”, and, if necessary, “ Including a preforming step.

(Matte body creation process)
In the mat body creation step, the mat body is created by mixing wood fibers and polylactic acid aliphatic polyester fibers. The “mat body” refers to all of a mixture of wood fibers and polylactic acid aliphatic polyester fibers. This “matte body” can be created, for example, by the following method.
In the first example of the mat body producing method, first, a wood-based fiber and a polylactic acid-based aliphatic polyester fiber are mixed to create a laminate (web). In order to create a laminate, a known lamination method such as a card method, a fleece method, or an airlay method can be used. Next, the wood fiber and the polylactic acid aliphatic polyester fiber are entangled by using a known entanglement technique such as needle punching. Thereby, it is possible to create a mat body in which wood-based fibers and polylactic acid-based aliphatic polyester fibers are uniform and entangled with high density.
In the second example, polylactic acid aliphatic polyester fibers are gradually added to the wood fibers at the time of defibrating the wood fibers. Thereby, polylactic acid type | system | group aliphatic polyester fiber can be uniformly mixed with respect to wood type fiber. Next, the mat body can be formed by entanglement of these fibers by needle punching or the like, or by compressing these fibers so that they can be packed and held in a single shape.

  The mixing ratio of the wood fiber and the polylactic acid aliphatic polyester fiber is not particularly limited, but the higher the ratio of the polylactic acid aliphatic polyester fiber, the weight of the wood fiber molded body molded after heating and pressurizing Will increase. On the other hand, if the amount of polylactic acid-based aliphatic polyester fiber is too small, the function as a binder is not sufficiently exhibited, and the bond between the wood-based fibers is weakened. There is a possibility. Therefore, the polylactic acid aliphatic polyester fiber is preferably 10% by weight or more and 50% by weight or less, and more preferably 30% by weight or more and 50% by weight or less based on the weight of the entire mat body. When the mixing ratio of the polylactic acid-based aliphatic polyester fibers is within this range, sufficient bonding between the wooden fibers can be achieved, and an increase in the weight of the wooden fiber molded body can be suppressed.

(Pre-molding material creation process)
In the pre-molding material creation step, a compatible copolymer is applied to the mat body. The compatible copolymer may be applied to the mat body as it is, but is preferably applied in a state dissolved or dispersed in water or an organic solvent. The mat body after the compatible copolymer is applied is referred to as “pre-molding material” in the present specification.
The compatible copolymer can be used by appropriately adjusting the concentration, viscosity, etc. by dissolving or dispersing in water or an organic solvent in consideration of workability when applied to the mat body.
The compatible copolymer may be applied to the mat body by any method such as spraying, dipping, or coating. However, in order to uniformly apply the mat copolymer to the mat body, spray the compatible copolymer or the like. And preferably applied by spraying.

The method for producing a wood-based fiber molded body according to the present invention is characterized in that after a mat body is prepared, a compatible copolymer is imparted to the mat body.
That is, as a method for uniformly adding the compatible copolymer to the polylactic acid-based aliphatic polyester, for example, the polylactic acid-based aliphatic polyester is compatible with the polylactic acid-based aliphatic polyester at a stage before fiberizing the polylactic acid-based aliphatic polyester. A method of adding a soluble copolymer in advance may be considered. However, in this case, the molecular weight of the polylactic acid-based aliphatic polyester increases and the viscosity increases at the stage of heating to make the polylactic acid-based aliphatic polyester into fibers, and the resin clogs the pores during spinning. There is a problem that defects such as yarn breakage and spinning speed may occur. Therefore, in the present invention, a polylactic acid-based aliphatic polyester is made into a fiber, and a mat body is prepared by mixing wood-based fibers and polylactic acid-based aliphatic polyester fibers, and a copolymer compatible with the mat body. Is granted. According to this method, since the compatible copolymer is held in the gap between the wood fiber and the polylactic acid aliphatic polyester fiber, the compatible copolymer is evenly contacted with both fibers. As a result, the effect of increasing the bond strength between the wood fiber and the polylactic acid aliphatic polyester is obtained by the action of the compatible copolymer when the pre-molding material is heated in the molding process.

  Cellulose, which is the main component of the wood fiber, has the property that, after containing water, the water evaporates, so that crystallization proceeds and rigidity is improved. Therefore, if moisture is given to the mat body together with the compatible copolymer, the rigidity of the wood fiber is improved and the strength of the molded body is improved when pressurized while heating in the next molding step. be able to. Therefore, the compatible copolymer is preferably applied to the mat body together with moisture after being dissolved in water to form an aqueous solution. In addition, the use of an aqueous solution is superior in that the environmental load of the manufacturing process can be reduced as compared with the case of using an organic solvent. The amount of the compatible copolymer applied to the mat body is not particularly limited, but is preferably as small as possible within the range in which the effect of the application can be obtained. For example, the blending ratio of the compatible copolymer is preferably 1.0% by weight or more and 10.0% by weight or less with respect to the weight of the polylactic acid-based aliphatic polyester fiber.

(Molding process)
In the molding step, the pre-molding material obtained in the above-described step is heated to a temperature at which the polylactic acid aliphatic polyester is in a softened state or a molten state, and pressure-molded by a known method. A known press machine or the like can be used for pressure molding. Thereby, the wood type fiber molded object shape | molded by desired shapes, such as board shape, can be obtained.

  In the molding step, when the pre-molding material is heated to a predetermined temperature, the polylactic acid-based aliphatic polyester fibers added to the pre-molding material are softened and melted. At this time, since the compatible copolymer is given to the material before molding, the compatible copolymer functions as a crosslinking agent that binds the wood fiber and the polylactic acid aliphatic polyester. As a result, the wood fiber and the polylactic acid aliphatic polyester are bonded via the compatible copolymer, and therefore, a three-dimensional bond structure is formed by these three components, and the molded product is obtained by swelling the wood fiber. Can be prevented from expanding. Further, the moisture resistance of the wood-based fiber molded body is remarkably improved by firmly bonding the wood-based fiber and the polylactic acid-based aliphatic polyester via the compatible copolymer.

(Preliminary molding process)
In the method for producing a wood-based fiber molded body according to the present invention, a preforming step can be performed between the pre-molding material creation step and the molding step. In this preforming step, the pre-molding material is compressed by pressurizing the pre-molding material using a press or the like. Thereby, the volume (bulk) of the material before shaping can be reduced.
By performing the preforming step, the volume of the pre-molding material can be reduced. This facilitates transportation and storage of the pre-molding material. In this case, it is possible to share the manufacturing process in which the process up to the process of creating the pre-molding material is performed in a certain place, and the process of pressurizing and molding the pre-molding material is performed in another place. For example, a production system is realized in which the process to create the pre-molding material is carried out overseas, the pre-molding material is imported by shipping, and the process of finally molding the wood-based fiber molded body is carried out in Japan. Is possible. Thereby, it becomes possible to mass-produce the wood-based fiber molded body with high efficiency.
In the preforming step, the pre-molding material may be pressurized while being heated. In this case, the heating temperature at the time of preforming is preferably a temperature at which the polylactic acid aliphatic polyester melts.

  In addition, in the manufacturing method of the wood type fiber molded object which concerns on this invention, of course, you may add another auxiliary material further. For example, it is possible to add a polyester resin modifier or the like in order to prevent degradation due to hydrolysis of polylactic acid-based aliphatic polyester. Examples of such modifiers include reagents (catalysts) that can accelerate the dehydration reaction such as carbodiimides such as dicyclohexylcarbodiimide. Such a modifier may be added to the molten resin of the polylactic acid aliphatic polyester in advance, or may be appropriately applied in the molding process by spraying the mat body in a state of being dissolved or dispersed in a solvent or the like. It can be applied at the previous intermediate material stage.

  As described above, according to the method for producing a wood fiber molded body according to the present invention, the binding strength between the wood fiber and the polylactic acid aliphatic polyester is increased by causing the compatible copolymer to act. The molecular weight of the polylactic acid-based aliphatic polyester can be increased. As a result, it is possible to obtain a wood-based fiber molded body having high physical strength and excellent moisture resistance.

Hereinafter, more specific examples of the present invention will be described.
Example 1
A fiber collected from kenaf bast was prepared as a wood fiber, and polylactic acid (L body 95% or more) was prepared as a polylactic acid polyester. Polylactic acid (L body 95% or more) was made into a fiber by a known spinning method, mixed and laminated so that the weight ratio of kenaf fiber: polylactic acid fiber was 70:30, and a mat body was prepared.
Separately from this, a polymerizable copolymer (hereinafter referred to as copolymer) in which the first polymerizable monomer is methoxypolyethylene glycol mono (meth) acrylate and the second polymerizable monomer is glycidyl (meth) acrylate. A 1.5% by weight aqueous solution of union A) was prepared.
This aqueous solution was applied to the mat body by spraying so that the ratio of the copolymer A to the polylactic acid fiber was 5.0% by weight, thereby preparing a pre-molding material.
The prepared pre-molding material is sandwiched between press dies whose press surfaces are heated to 230 ° C., pressurized while being heated to a pressure of 24 kgf / cm ² and an internal temperature of 210 ° C., and a preform with a thickness of 2.5 mm It was created.
The preform is heated in an oven heated to 230 ° C. for 170 seconds, the internal temperature is raised to 210 ° C., the preform is sandwiched between press dies, and compressed at a pressure of 36 kgf / cm ² for 60 seconds. A wood-based fiber molded body was prepared.

(Example 2)
The polylactic acid (L body 95% or more) used in Example 1 was made into a fiber by a known spinning method, mixed and laminated so that the weight ratio of kenaf fiber: polylactic acid fiber was 70:30, and a mat body was formed. Created.
Separately, an aqueous solution containing 1.5% by weight of copolymer A and 0.3% by weight of “carbodilite E-04” (manufactured by Nisshinbo Co., Ltd.), which is a polyimide compound, was prepared.
This aqueous solution is applied to the mat body by spray so that the ratio of the copolymer A to the polylactic acid fiber is 5.0% by weight and the ratio of the carbodilite E-04 to the polylactic acid fiber is 1.0% by weight. Then, a pre-molding material was prepared.
The prepared pre-molding material is sandwiched between press dies whose press surfaces are heated to 230 ° C., pressurized while being heated to a pressure of 24 kgf / cm ² and an internal temperature of 210 ° C., and a preform with a thickness of 2.5 mm It was created.
The preform is heated in an oven heated to 230 ° C. for 170 seconds, the internal temperature is raised to 210 ° C., the preform is sandwiched between press dies, and compressed at a pressure of 36 kgf / cm ² for 60 seconds. A wood-based fiber molded body was prepared.

(Comparative Example 1)
Using the same method as in Example 1, a wood-based fiber molded body was prepared.
However, it was prepared without applying the aqueous solution of copolymer A to the mat body. Moreover, what added 1.0 weight% of "carbodilite HMV-8CA" (made by Nisshinbo Co., Ltd.) which is a polyimide compound was used for the polylactic acid fiber.

(Comparative Example 2)
Using the same method as in Comparative Example 1, a wood-based fiber molded body was prepared.
However, the mat body used was a mixture of kenaf fibers and polylactic acid fibers in a weight ratio of 50:50.

(Evaluation of heat and humidity resistance)
First, the thickness, bending strength, and weight average molecular weight of the polylactic acid resin in each sample of Examples 1 and 2 and Comparative Examples 1 and 2 were measured. The plate thickness and bending strength were measured from a rectangular test piece having a width of 50 mm and a length of 150 mm. The bending strength is that the test piece is supported by two fulcrums so that the distance between the fulcrums is L = 100 mm, a load of 50 mm / min is applied to the center position between both fulcrums, and the test piece is immediately before breaking. The maximum load P was measured. The curvature radii of the two fulcrums and the load application point were 3.2 mm. The bending strength was calculated by the following formula.
Bending strength (MPa) = 3PL / 2Wt ²
Where P: Maximum load
L: Distance between fulcrums
W: Width of test piece (50 mm)
t: thickness of the test piece (2.3 mm)

Next, after placing each test piece in a room at a temperature of 50 ° C. and a humidity of 95% RH and leaving it for 400 hours, the plate thickness and bending strength of each sample and the weight of the polylactic acid resin in the sample were measured in the same manner as described above. Average molecular weight was measured. Further, the bending strength retention rate and the plate thickness expansion rate were calculated from the following equations. Hereinafter, the test piece is identified as “before exposure” when the test piece is placed in a high-temperature and high-humidity room at a temperature of 50 ° C. and a humidity of 95% RH, and “after exposure” after being left in the room for 400 hours.
Bending strength retention ratio (%) = (δ ′ / δ) × 100
Where δ: Bending strength before exposure
δ ′: Flexural strength after exposure Plate thickness expansion rate (%) = (T′−T) / T × 100
T: Thickness of the specimen before exposure
T ′: thickness of test piece after exposure

  The measured values of each sample are shown in Table 1.

  As shown in Table 1, in the production methods of Examples 1 and 2, compared to Comparative Example 1 in which the weight ratio of kenaf fiber: polylactic acid fiber is 70:30, the bending strength and bending strength before exposure are the same. A wood-based fiber molded body having a significantly high thickness retention and a remarkably low plate thickness expansion rate was obtained. Further, even when compared with Comparative Example 2 in which the weight ratio of polylactic acid fiber (binder fiber) is high and the weight ratio of kenaf fiber: polylactic acid fiber is 50:50, the bending strength and the bending strength are maintained before exposure. A wood-based fiber molded body having a high rate and a low sheet thickness expansion coefficient was obtained. From this result, after applying a compatible copolymer to the mat body, heat compression molding does not increase the binder resin, it is lightweight and high in strength, and is resistant to strength deterioration and deformation even after exposure, and has moisture resistance. It was revealed that a high wood fiber molded body can be obtained.

  Moreover, in Example 2, the wood type fiber molded object with a higher bending strength retention than Example 1 was obtained. From this result, it became clear that by adding a compatible copolymer and a polyimide compound in combination, a wood-based fiber molded body that exhibits a synergistic effect and is more excellent in moisture resistance can be obtained. This is considered to be because the hydrolysis of polylactic acid was suppressed because “carbodilite E-04”, which is a polyimide compound, also has an end-capping agent effect.

  The weight average molecular weights of the polylactic acid resins of the wood fiber molded bodies obtained in Examples 1 and 2 were significantly higher than those in Comparative Examples 1 and 2, and a tendency to increase rather than decrease after exposure was observed. . From this result, it was found that the molecular weight of polylactic acid increases when a compatible copolymer is applied to the polylactic acid resin and heated. By increasing the molecular weight, the strength of polylactic acid itself is improved, and it is presumed that it is effectively involved in improving the strength of the wood-based fiber molded body.

  The bending strength before exposure of the wood-based fiber molded bodies obtained in Examples 1 and 2 was found to be higher than the bending strength before exposure of the wood-based fiber molded bodies obtained in Comparative Examples 1 and 2. . This is because in Examples 1 and 2, crystallization of cellulose contained in the wood fiber progressed by the evaporation of the moisture after the moisture was applied to the mat body, and the rigidity of the cellulose was improved. It is thought to be the cause. That is, in the case of providing a compatible copolymer to the mat body, rather than applying the compatible copolymer as it is, it is preferable to apply the compatible copolymer in water after dissolving it in water. It has been found that a wood fiber molded product having higher strength and excellent moisture resistance can be obtained.

It is a flowchart which shows the manufacturing method of the wood type fiber molded object which concerns on this invention.

Claims (8)

A method for producing a wooden fiber molded body,
A mat body creating step of creating a mat body by mixing wood fiber and polylactic acid aliphatic polyester fiber;
A pre-molding material creation step of creating a pre-molding material by applying a compatible copolymer to the mat body;
And a molding step of heating and pressurizing the pre-molding material at a temperature at which the polylactic acid-based aliphatic polyester fiber is in a softened state or a melted state to form into a predetermined shape. Method.   The method for producing a wood-based fiber molded body according to claim 1, further comprising a preforming step of preforming the material before molding between the pre-molding material creation step and the molding step. The compatible copolymer includes a copolymer obtained by polymerizing the first polymerizable monomer and the second polymerizable monomer,
The first polymerizable monomer has a polymerizable double bond portion and a hydrophilic group,
The said 2nd polymerizable monomer is a manufacturing method of the wood type fiber molded object of Claim 1 or Claim 2 which has a polymerizable double bond part and an epoxy group.   The method for producing a wood-based fiber molded body according to claim 3, wherein the first polymerizable monomer has a polyalkylene oxide chain as a hydrophilic group.   The woody fiber according to claim 3 or 4, wherein the first polymerizable monomer is methoxypolyethylene glycol mono (meth) acrylate and the second polymerizable monomer is glycidyl (meth) acrylate. Manufacturing method of a molded object.   The method for producing a wood-based fiber molded body according to any one of claims 1 to 5, wherein, in the pre-molding material creation step, the compatible copolymer is applied to the mat body in a state of an aqueous solution. .   The method for producing a wood-based fiber molded body according to any one of claims 1 to 6, wherein the wood-based fiber is a fiber derived from kenaf. The method for producing a woody fiber molded body according to any one of claims 1 to 7, wherein the polylactic acid-based aliphatic polyester fiber is a fiber made of polylactic acid.

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