JP2019065130A - Thermoplastic resin composition and manufacturing method therefor - Google Patents

Abstract

To provide a thermoplastic resin composition having higher strength while providing a plant fiber conventionally used as a reinforcement material of a resin, and a manufacturing method therefor.SOLUTION: Thee is provided a thermoplastic resin composition containing a thermoplastic resin, a plant fiber and a binder, in which the binder is a thermoplastic resin composition consisting of a melamine resin and/or a polyamideamine resin. There is provided a manufacturing method of the thermoplastic resin composition, having a process for preparing a mixture containing the plant fiber and the binder, a process for adding the mixture to the thermoplastic resin, in which the process for preparing the mixture includes a process for mixing the plant fiber and the binder, or a process for preparing waste paper pulp derived from waste paper containing the binder, and the binder consists of the melamine resin and/or the polyamideamine resin.SELECTED DRAWING: None

Description

  The present invention relates to a thermoplastic resin composition and a method for producing the same.

  In order to obtain a reinforcing effect of resin, reinforced resin using inorganic fiber such as glass fiber or carbon fiber as a reinforcing material is widely used. However, since the specific gravity of inorganic fibers and carbon fibers is heavy, the specific gravity of the reinforcing resin is also heavy, and it is insufficient from the aspect of environmental consideration. In order to obtain a reinforcing effect of resin among environmentally friendly materials, conventionally, a composite of kneaded pulp and waste paper and thermoplastic resin is known.

  Although the thermoplastic resin composition which mix | blended paper or crushed waste paper is proposed by the reference document 1, the reinforcement effect of resin is inadequate. Moreover, although the method of knead | mixing a pulp sheet or a piece of paper with a thermoplastic resin, and disintegrating a pulp is proposed by the cited reference 2, the strength of the interface of a pulp and resin is only disperse | distributed to a thermoplastic resin. And insufficient reinforcement effect can be obtained. In the cited reference 3, after chemically modifying the pulp, it is possible to disintegrate to cellulose nanofibers with relatively low energy and to improve adhesion of the interface between the cellulose and the resin, and also to improve the reinforcing effect by kneading the resin with the resin. Has been proposed. However, since the method of reference 3 uses an organic solvent for chemical modification of pulp, the production process is complicated in terms of solvent recovery. In addition, it is necessary to cope with the equipment in terms of sanitation of the manufacturing workers, and as a result, there is a disadvantage that the cost is high.

JP 2007-260941 A JP, 2009-197044, A JP, 2016-176052, A

  The main problem to be solved by the present invention is to provide a thermoplastic resin composition having higher strength and a method for producing the same while using a conventionally used plant fiber as a reinforcing material for resin. Another object of the present invention is to make it possible to reuse as a material of paper and paperboard with increased water resistance to which melamine resin or polyamidoamine resin as a wet strength agent, which has been difficult to recycle conventionally, has been added.

  The present invention for solving the above problems is a thermoplastic resin composition comprising a thermoplastic resin, a plant fiber and a binder, wherein the binder is a melamine resin and / or a polyamide amine resin.

  According to the thermoplastic resin composition, by using plant fibers as a reinforcing material for the thermoplastic resin, it is possible to reduce the weight of the obtained thermoplastic resin composition, and to use a specific binding agent in combination. The reinforcing effect can be further enhanced while using vegetable fibers which inherently have a weak bonding force with the thermoplastic resin.

  The thermoplastic resin is a combination of one or more selected from polyethylene, polypropylene, polyester, nylon and polyacetal, and the main component of the vegetable fiber is natural cellulose, and the above-mentioned binding to 100 parts by mass of the vegetable fiber The content of the agent is preferably 0.5 parts by mass or more and 20 parts by mass or less. As the thermoplastic resin, one or two or more selected from polyethylene, polypropylene, polyester, nylon, polyacetal having high versatility can be suitably used, so that cost increase and the like can be suppressed. In addition, natural cellulose having high biodegradability is preferable as a main component of plant fibers from the viewpoint of environmental protection. In addition, when the content of the binder with respect to the vegetable fiber is 0.5% by mass or more and 20% by mass or less, the reinforcing effect can be further enhanced while suppressing the cost increase.

  It is preferable that the volume average particle diameter of the said vegetable fiber is 5 micrometers or more and 300 micrometers or less, and the said binder is a melamine formaldehyde resin and / or polyamidoamine epichlorohydrin resin. Thus, the reinforcing effect can be further enhanced by using a plant fiber having a volume average particle diameter smaller than that of a conventional plant fiber in the above range. If the volume average particle size is less than 5 μm, the energy cost for setting the particle size to less than 5 μm may be high and the cost performance may be inferior.

  The present invention for solving the above problems comprises a step of preparing a mixture containing plant fibers and a binder, and a step of adding the above mixture to a thermoplastic resin, and the step of preparing the above mixture is a plant fiber The thermoplastic resin composition comprising the step of mixing the binder and the binder, or the step of preparing the waste paper pulp derived from waste paper containing the binder, wherein the binder comprises a melamine resin and / or a polyamide amine resin Manufacturing method.

  According to the manufacturing method, before mixing the plant fiber and the binding agent with the thermoplastic resin, the waste paper pulp derived from waste paper containing the binding agent, or a mixture of the plant fiber and the binding agent is prepared. By adding this to the thermoplastic resin, the binder is fixed in advance to the outer surface of the vegetable fiber, and in the addition step to the thermoplastic resin, uniform dispersion and fixation with the thermoplastic resin can be achieved, which is high. It is possible to obtain a thermoplastic resin having strength. In addition, it is possible to reuse as a material of paper and paperboard with increased water resistance to which melamine resin or polyamidoamine resin as a wet strength agent, which has been difficult to recycle conventionally, is added. Moreover, the said manufacturing method has an advantage that it can manufacture simply and cheaply and it is hard to produce the problem of a solvent treatment. According to the said manufacturing method, the lightweight resin composition in consideration of environment can be obtained.

  The said manufacturing method is the process of adjusting the volume average particle diameter of a mixture to 5 micrometers or more and 300 micrometers or less by the physical disintegration process with respect to the said mixture, and the said mixture is the process of adding before the process of said addition. It is preferable to have the process of knead-processing the added thermoplastic resin. Thus, after adjusting the volume average particle diameter of the mixture to 5 μm or more and 300 μm or less, the thermoplastic resin composition is added to the thermoplastic resin and subjected to a kneading treatment to obtain a thermoplastic resin composition having a more uniform composition and high strength. Can.

  According to the present invention, it is possible to provide a thermoplastic resin composition having higher strength and a method for producing the same while using plant fibers as a reinforcing material for resin. In addition, it is possible to reuse as a material of paper and paperboard with increased water resistance to which melamine resin or polyamidoamine resin as a wet strength agent, which has been difficult to recycle conventionally, is added.

<Thermoplastic resin composition>
The thermoplastic resin composition of one embodiment of the present invention contains a thermoplastic resin, plant fibers and a binder.

(Thermoplastic resin)
Examples of thermoplastic resins include polyolefins such as polyethylene (PE) and polypropylene (PP), polyesters such as aliphatic polyester resins and aromatic polyester resins, acrylic resins such as polystyrene, polymethacrylates and polyacrylates, nylons (polyamides) , Polycarbonate, polyacetal and the like. A thermoplastic resin can be used 1 type or in mixture of 2 or more types.

  The thermoplastic resin is preferably a combination of one or more selected from polyolefins, polyesters, nylons and polyacetals, and more preferably contains at least one of a polyolefin and a polyester resin. As a polyolefin, a polypropylene is preferable.

  Examples of polyesters include aliphatic polyesters such as polylactic acid and polycaprolactone, and aromatic polyesters such as polyethylene terephthalate. As the polyester, a biodegradable polyester resin (also referred to simply as "biodegradable resin") is preferable.

  As biodegradable resin, 1 type (s) or 2 or more types can be selected and used, for example from hydroxycarboxylic acid type aliphatic polyester, caprolactone type aliphatic polyester, dibasic acid polyester etc., for example.

  As the hydroxycarboxylic acid-based aliphatic polyester, for example, homopolymers of hydroxycarboxylic acids such as lactic acid, malic acid, glucose acid, 3-hydroxybutyric acid and the like, or a copolymer using at least one of these hydroxycarboxylic acids 1 type or 2 types or more can be selected and used from coalescence etc. Among them, polylactic acid, a copolymer of lactic acid and a hydroxycarboxylic acid other than lactic acid, polycaprolactone, and a copolymer of at least one of the above hydroxycarboxylic acids and caprolactone are preferable, and polylactic acid is more preferable.

  As lactic acid, for example, L-lactic acid, D-lactic acid and the like can be used, and these lactic acids may be used alone or in combination of two or more.

  As the caprolactone based aliphatic polyester, for example, one or more selected from a homopolymer of polycaprolactone, a copolymer of polycaprolactone and the like and the above hydroxycarboxylic acid, and the like can be selected and used.

  As a dibasic acid polyester, 1 type (s) or 2 or more types can be selected and used among polybutylene succinate, a polyethylene succinate, a polybutylene adipate etc., for example.

  As a minimum of content of a thermoplastic resin in the thermoplastic resin composition concerned, 10 mass% is preferred, 30 mass% is more preferred, and 40 mass% is still more preferred. By making content of a thermoplastic resin more than the said lower limit, sufficient thermoforming property etc. can be exhibited and intensity | strength can be raised. On the other hand, as an upper limit of this content, 90 mass% is preferable, 70 mass% is more preferable, and 50 mass% is more preferable. By setting the content of the thermoplastic resin to the above upper limit or less, a sufficient amount of plant fibers, a binder and the like can be contained, and the strength can be further enhanced.

(Plant fiber)
As said vegetable fiber, the pulp fiber whose main component is natural cellulose is used normally suitably. In addition, a main component means the component with most content on a mass basis. 60 mass% is preferable, as for the minimum of content of natural cellulose in vegetable fiber, 80 mass% is more preferable, and 90 mass% is more preferable. The raw material of the vegetable fiber may be herbaceous such as softwood, hardwood, bamboo, rattan or recycled paper. However, wood-derived or waste-paper-derived pulp is preferable in terms of availability of raw materials and the like. Usually, desired vegetable fibers can be obtained by, for example, refining pulp.

Examples of pulp used as a raw material of vegetable fiber include hardwood bleached kraft pulp (LBKP), hardwood kraft pulp (LKP) such as hardwood unbleached kraft pulp (LUKP), softwood bleached kraft pulp (NBKP), softwood unbleached kraft pulp (NUKP) ) Chemical pulp such as softwood kraft pulp (NKP);
Stone Grand Pulp (SGP), Pressed Stone Grand Pulp (PGW), Refiner Grand Pulp (RGP), Chemi Grand Pulp (CGP), Thermo Grand Pulp (TGP), Grand Pulp (GP), Thermo Mechanical Pulp (TMP), Mechanical pulp such as chemithermomechanical pulp (CTMP), bleached thermomechanical pulp (BTMP);
Waste paper pulp produced from tea waste paper, kraft envelope waste paper, magazine waste paper, newspaper waste paper, flyer waste paper, office waste paper, corrugated waste paper, top white waste paper, Kent waste paper, imitation waste paper, ground waste paper, waste paper waste paper, etc .; waste paper pulp Deinked deinked pulp (DIP) etc. may be mentioned.

  Among these, NBKP and waste paper pulp are preferred. These may be used alone or in combination of two or more.

  The pulp used as a raw material of vegetable fiber may be subjected to chemical pretreatment. Examples of the chemical pretreatment include an acid such as sulfuric acid, a hydrolysis treatment using an enzyme or the like, an oxidation treatment using an oxidant such as ozone, and the like. In addition, pretreatment such as phosphate esterification, TEMPO oxidation, or acetylation may be performed. However, since the cost increases if the chemical modification is performed, hydrolysis treatment with an acid or enzyme or oxidation treatment with ozone or the like is preferable. Hydrolysis treatment and oxidation treatment decompose the non-crystallized area of hemicellulose and cellulose possessed by pulp, and as a result, energy of beating treatment and physical disintegration treatment (refining treatment) can be reduced, and fiber homogeneity can be reduced. And dispersion can be improved. In addition, those treated with hydrolysis treatment and oxidation treatment have high dispersibility because the ratio of the cellulose crystal region considered to be rigid and having a low water retention ratio to the whole fiber is high because the molecular chains are aligned and rigid. A thermoplastic resin composition having higher target strength is obtained.

  In addition, the pulp may be subjected to an alkali treatment as a chemical pretreatment. The alkali treatment partially dissociates the hydroxyl groups of hemicellulose and cellulose possessed by the pulp, and the anionization of the molecules weakens the intramolecular and intermolecular hydrogen bonds, which has the effect of promoting the dispersion of the pulp in the beating process. . As the alkali, an organic alkali such as sodium hydroxide, lithium hydroxide, potassium hydroxide, aqueous ammonia solution, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, etc. is used. It is preferable to use sodium hydroxide from the viewpoint of production cost.

  As a maximum of volume average particle diameter of the above-mentioned vegetable fiber, 300 micrometers is preferred, 250 micrometers is more preferred, 200 micrometers is still more preferred, and 100 micrometers is still more preferred. On the other hand, the lower limit of the volume average particle diameter may be 1 μm, preferably 5 μm, more preferably 10 μm, still more preferably 20 μm, and still more preferably 50 μm. Thus, the reinforcing effect can be further enhanced by using a vegetable fiber having a relatively fine volume average particle diameter in the above range. In addition, with the volume average particle diameter of the above-mentioned vegetable fiber, based on ISO-13320 (2009), it measures using a particle size distribution measuring device (for example, "Laser diffraction and scattering type particle size distribution measuring device" of Seishin Enterprise Co., Ltd.) Median diameter (D50) obtained from the volume-based particle size distribution.

  As a minimum of content of vegetable fiber in the thermoplastic resin composition concerned, 2 mass% is preferred, 5 mass% is more preferred, 10 mass% is more preferred, and 30 mass% is still more preferred. By setting the content of the plant fiber to the above lower limit or more, the strength can be further enhanced. On the other hand, as a maximum of this content, 70 mass% is preferred, 60 mass% is more preferred, and 50 mass% is more preferred. By making content of a vegetable fiber below the said upper limit, a sufficient amount of thermoplastic resins etc. can be contained and a moldability etc. can be improved.

(Binding agent)
The binder is composed of melamine resin and / or polyamidoamine resin. It is presumed that this binder can enhance the compatibility and the bonding between the thermoplastic resin and the plant fiber, thereby increasing the strength of the thermoplastic resin composition. In the thermoplastic resin composition, the binder is presumed to be present between the thermoplastic resin and the plant fiber, or attached to at least a part of the surface of the plant fiber. .

  The type of the above-mentioned melamine resin is not particularly limited. For example, melamine-formaldehyde resin such as methylated melamine obtained by reacting melamine and formaldehyde, melamine which can be cocondensed with such melamine and formaldehyde as a part of melamine Examples thereof include melamine-formaldehyde-based cocondensation resins obtained by substitution with components for co-condensation. Among the melamine resins, a melamine-formaldehyde resin is preferable as the binder.

  The type of the component for the melamine co-condensation is not particularly limited. For example, ureas such as urea, ethylene urea and thiourea; benzoguanamine, acetoguanamine, phenylacetoguanamine, formulanamine such as holm guanamine, CTU guanamine and the like; And amino compounds such as dicyandiamide and paratoluenesulfonamide; phenols such as phenol, cresol, xylenol, ethylphenol, butylphenol and bisphenol A; and other compounds for melamine co-condensation such as xylene and sucrose. Such components for melamine co-condensation can be used singly or in combination of two or more.

  A melamine resin is a component that reacts with the hydroxyl groups and carboxyl groups of plant fibers (cellulose) to strengthen the bonds between the fibers, and also suppresses the penetration of water into the bonds between the fibers and improves the wet strength of the paper. Conceivable. For this reason, when the said thermoplastic resin composition contains a melamine resin, the compatibility and the bondability with the thermoplastic resin and vegetable fiber which usually have a tendency of hydrophobicity can be improved, and strength can be improved.

  A polyamide amine resin is obtained by reacting an epihalohydrin represented by epichlorohydrin with nitrogen of a main chain obtained by condensing a polyvalent acid and a polyamine polyalkylpolyamine or urea, and the polyamidepolyamine-epihalohydrin resin This is a generic term for resins having both a cationic quaternary amine and a reactive functional group represented by polyamidepolyaminepolyurea-epihalohydrin resins. Among the polyamidoamine resins, polyamidoamine epichlorohydrin resins are preferred as the binder.

  The polyamidoamine resin is preferably cation-modified so that it can be easily fixed to plant fibers, and the reactive functional group reacts with the hydroxyl group or carboxyl of the cellulose to strengthen the bond between the fibers and, at the same time, between the fibers of the pulp It is considered to be a component that suppresses the infiltration of water into bonds and improves the wet strength of paper. For this reason, when the said thermoplastic resin contains polyamidoamine resin, the compatibility and the bondability of the thermoplastic resin and vegetable fiber which are in the tendency of a hydrophobicity can be improved normally, and strength can be improved.

  The reactive functional group is preferably a cyclic amino group having a four-membered ring or less represented by an aziridinium group or azetidinium group, and more preferably an azetidinium group having both the properties of a quaternary amine and the properties of a reactive functional group. In addition, when making a reactive group into an aziridinium group, the nitrogen which comprises an aziridinium group may be denatured to the quaternary amine which shows cationicity. Representative polyamidoamine resins include polyamidoamine epichlorohydrin resins (PAEs). The polyamide epichlorohydrin resin has reactive functional groups such as azetidinium and aziridinyl groups.

  The lower limit of the content of the binder with respect to 100 parts by mass of the vegetable fiber may be 0.1 part by mass or 0.3 parts by mass, but is preferably 0.5 parts by mass, and more preferably 1 part by mass. Preferably, 2 parts by mass is more preferable. By setting the content of the binder to the above lower limit or more, the reinforcing effect can be further enhanced. On the other hand, as an upper limit of this content, 20 mass parts is preferred, 15 mass parts is more preferred, 10 mass parts is still more preferred, and 5 mass parts is still more preferred. By setting the content of the binding agent to the above-mentioned upper limit or less, it is possible to suppress the ceiling effect of the increase in the binding agent and to suppress the cost. Moreover, the production efficiency at the time of dehydration and drying in the manufacturing method to be described later can be enhanced by setting the content of the binder to the upper limit or less.

(Compatibilizer)
The thermoplastic resin composition preferably further contains a compatibilizer. The compatibilizer can enhance the compatibility, the dispersibility, and the like of the thermoplastic resin and the plant fiber, and as a result, can increase the strength.

  As a compatibilizer, a polymer having an acid anhydride group in a side chain is preferable. Specifically, polymers obtained by graft-modifying a polymer with an acid anhydride are preferred. As the acid anhydride, for example, maleic anhydride, itaconic anhydride, citraconic anhydride, citric anhydride and the like can be mentioned, with preference given to maleic anhydride. As a specific example of such a compatibilizer, carboxylic anhydride modified polyolefins, such as maleic anhydride modified polypropylene etc., etc. can be mentioned.

  The lower limit of the content of the compatibilizer is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, and still more preferably 1 part by mass with respect to 100 parts by mass of the thermoplastic resin. On the other hand, as an upper limit of this content, 10 mass parts is preferred, 8 mass parts is more preferred, and 6 mass parts is still more preferred. When the content of the compatibilizer is in the above range, the dispersibility of plant fibers and the like can be further improved, and the strength of the thermoplastic resin composition, in particular, the bending strength can be improved.

(Other ingredients)
The said thermoplastic resin composition may further contain another component in the range which does not inhibit the effect of this invention. An inorganic filler etc. can be mentioned as another component.

  Examples of the inorganic filler include simple substances, oxides of metallic elements in Groups I to VIII of the periodic table, such as Fe, Na, K, Cu, Mg, Ca, Zn, Ba, Al, Ti, etc. A hydroxide, a carbon salt, a sulfate, a silicate, a sulfite, various clay minerals etc. which consist of these compounds can be illustrated. Specifically, for example, barium sulfate, calcium sulfate, magnesium sulfate, sodium sulfate, calcium sulfite, zinc oxide, silica, ground calcium carbonate, light calcium carbonate, aluminum borate, alumina, iron oxide, calcium titanate, aluminum hydroxide Examples thereof include magnesium hydroxide, calcium hydroxide, sodium hydroxide, magnesium carbonate, calcium silicate, clay wollastonite, glass beads, glass powder, silica sand, vermiculite, quartz powder, diatomaceous earth, white carbon and the like.

  However, as an upper limit of the content of other components other than the thermoplastic resin, the plant fiber, the binder and the compatibilizer in the thermoplastic resin composition, 30 parts by mass may be preferable, and 10 parts by mass is preferable. It may be more preferable, and 1 part by mass may be more preferable. By reducing the content of the other components, the interaction of the thermoplastic resin, the plant fiber, the binder and the like can function more sufficiently, and the strength can be increased.

<Method of producing thermoplastic resin composition>
The manufacturing method of the said thermoplastic resin is not specifically limited, For example, although it can obtain by mixing a thermoplastic resin, a vegetable fiber, and a binder, it is preferable to manufacture with the following method.

That is, the method for producing a thermoplastic resin composition according to an embodiment of the present invention
Providing a mixture comprising plant fibers and a binding agent (A);
And (c) adding the above mixture to the thermoplastic resin.

Furthermore, the manufacturing method is
Prior to the step (C), a step (B) of adjusting the volume average particle diameter of the mixture to 5 μm or more and 300 μm or less by physical disintegration treatment of the mixture;
And (k) kneading the thermoplastic resin to which the mixture has been added after the step (C).
Each step will be described in detail below in the order of steps.

(Step (A))
In the step (A), a mixture containing plant fibers and a binding agent is prepared. This process (A) includes either of the following processes (A1) and processes (A2).
Step (A1) A step of mixing plant fiber and a binding agent Step (A2) A step of preparing waste paper pulp derived from waste paper containing a binding agent

(Step (A1))
The said process (A1) can be performed by the method similar to the method of manufacturing the general paper containing a melamine resin and / or polyamidoamine resin. Hereinafter, the step (A1) will be described.

  Paper sheets are obtained by making vegetable fibers. The vegetable fiber is preferably made of the above-described pulp as a raw material.

  As an upper limit of the freeness of the vegetable fiber provided to the said process (A1), 700 mL is preferable and 650 mL is more preferable. By making freeness below the said upper limit, the coupling | bonding between pulps can increase and it can improve the intensity | strength of a thermoplastic resin composition. On the other hand, the lower limit of the freeness is preferably 50 mL, more preferably 100 mL, even more preferably 200 mL, and even more preferably 300 mL, 400 mL or 500 mL. By setting the freeness to 50 mL or more, the dewatering treatment on the paper machine at the time of production is accelerated, and the productivity is enhanced. In addition, the said freeness is a value which measured the freeness with the Canadian standard freeness tester according to JIS-P8121 after disaggregating vegetable fiber with a standard disintegration machine based on JIS-P8220. is there.

  The freeness of plant fibers can be adjusted, such as by adjusting the beating conditions of the pulp. The beating of pulp can be appropriately performed using a beater, a single disc refiner, a double disc refiner, or a conical refiner generally used in paper production.

  For papermaking, dewatering and drying of vegetable fibers, it is preferable to use a pulp mill or paper machine used for producing paper. Although there is also a method of dewatering with a filter press etc., the filter press itself is inferior in productivity, and it is necessary to dry the water which could not be removed with the filter press, but in order to dry unshaped dewatered pulp There is nothing but drying with a hot air dryer, which results in an increase in cost.

  The wire of the paper machine may be a circular net, a long net, a short net, a gap former, etc. which are commonly used in the manufacture of paper, and a drying method is a multi-cylinder drier, a Yankee drier, a hot air drier etc. It can be used.

  The method of mixing the melamine resin and / or the polyamidoamine resin, which is a binder, may be a method of internally adding to paper, or the vegetable fibers may be sheeted and then impregnated or applied onto the sheet. The coating method is generally used for papermaking. A 2-roll size press, a gate roll coater, a rod metering coater, a blade coater, an air knife coater, a comma coater, etc. are used. In order to coat vegetable fiber uniformly, 2 roll size press and a blade coater are preferred.

The paper sheet containing the melamine resin and / or the polyamide amine resin obtained through such a step (A1) is the above mixture. As a maximum of the density of the above-mentioned paper sheet, 1 g / cm ³ is preferred, and 0.8 g / cm ³ is more preferred. Moreover, as a lower limit of the density of this paper sheet, 0.4 g / cm < ³ > is preferable and 0.6 g / cm < ³ > is more preferable. By setting the density of the paper sheet in the above range as described above, a uniform particle diameter can be obtained when subjected to the step (B). In addition, when this density exceeds the said upper limit, when the said paper sheet is provided to a process (B), since the bonding strength between vegetable fibers is too strong, crushing can not be performed uniformly but an uncrushed paper piece remains There is a case. On the other hand, if the density is less than the above lower limit, the bond between the fibers is weak, and the paper sheet is broken at the time of grinding, and the grinding efficiency is deteriorated.

  As in step (A1), by adding melamine resin and / or polyamide amine resin to plant fibers in advance and preparing a sheet with a paper machine, the above resin can be coated uniformly on the plant fiber surface efficiently, and the dryer By promoting the bond between the plant fiber and the resin using heat, the plant fiber can be efficiently dispersed uniformly in the thermoplastic resin, and the strength of the thermoplastic resin composition can be increased. The same effect can also be obtained by applying a melamine resin and / or a polyamide amine resin with a 2-roll size press or a blade coater or the like and drying after preparing a sheet of plant fibers in advance.

  Thus, in this step (A1), by bringing the binder (melamine resin and / or polyamidoamine resin) into contact with the surface of the plant fiber in advance, it is more efficient than adding the binder during kneading. Thus, compatibility and bondability of plant fibers in a thermoplastic resin can be efficiently enhanced at low cost.

(Step (A2))
Step (A2) is a step of preparing waste paper pulp derived from waste paper containing a binder, instead of producing a paper sheet containing a binder as in step (A1). This waste paper pulp is a mixture containing plant fibers and a binder. Such waste paper pulp is substantially manufactured through the step (A1) in the stage before becoming waste paper, and even if such waste paper pulp is used, the above-described effects similar to the above step (A1) You can get

  In addition, melamine resin and polyamidoamine resin are added as a wet strength agent in papermaking applications and are components capable of dramatically improving the water resistance of paper and paperboard, while the water resistance is too high. Because it is difficult to put paper or paperboard into water and break up to the state of pulp, it is difficult to recycle as a raw material for paper or paperboard. For this reason, thermal recycling is performed as a part of fuel, or treated as industrial waste. On the other hand, according to the said manufacturing method, it is possible to add the wet strength agent (melamine resin and / or polyamidoamine resin) and to effectively utilize the paper or paper board with improved water resistance as a reinforcing material for thermoplastic resin. Can.

(Step (B))
In the step (B), the volume average particle diameter of the mixture is adjusted to 50 μm or more and 300 μm or less by physical fibrillation treatment on the mixture (paper sheet or waste paper pulp). As a physical disintegration processing, dry grinding is mentioned. Dry grinding is preferable because the particle size becomes uniform. The grinding can be carried out using a mixer, a hammer mill, a cutter mill, a millstone-shaped mass colloider, etc., but it is preferable to use a hammer mill from the viewpoint of productivity and the like.

  The upper limit of the volume average particle diameter (D50) of the mixture subjected to physical disintegration treatment such as pulverization and the like that is subjected to the step (C) is preferably 300 μm, more preferably 250 μm, still more preferably 200 μm, and still more preferably 100 μm. . By setting the volume average particle diameter of the mixture to the above upper limit or less, the dispersibility can be enhanced and the reinforcing effect can be enhanced. On the other hand, the lower limit of the volume average particle diameter (D50) of this mixture is preferably 5 μm, more preferably 10 μm, still more preferably 20 μm, and still more preferably 50 μm. If the volume average particle size is too fine, the apparent bulk specific gravity may be lowered, and the work efficiency may be lowered, for example, it may be scattered in the air. The volume average particle diameter of the above mixture is measured using a particle size distribution measuring device (for example, “Laser diffraction / scattering type particle size distribution measuring device” by Seishin Enterprise Co., Ltd.) in accordance with ISO-13320 (2009). Mean the median diameter (D50) obtained from the volume-based particle size distribution.

The bulk density of the mixture subjected to physical disintegration treatment such as pulverization and subjected to the step (C) is preferably 100 g / m ³ or more. Thus, by having a certain bulk density, the injection efficiency at the time of mixing can be improved, and productivity can be improved. The upper limit of the bulk density, for example, ^{300g / m 3, 200g / m} 3 is preferred.

(Step (C))
In step (C), the above mixture is added to the thermoplastic resin. At this time, other components such as a compatibilizer and an inorganic filler may be added to the thermoplastic resin. The addition of each component may be simultaneous or separate.

(Step (D))
In the step (D), the thermoplastic resin to which the above mixture is added is subjected to a kneading treatment. This kneading process is usually melt kneading. Kneading may be carried out by a method of kneading fibers directly into pellets of thermoplastic resin, or by a method called solid-phase shearing method in which powder of thermoplastic resin and the above mixture are dispersed in water, dehydrated and dried, and then kneaded. good.

  The temperature at the time of the kneading treatment is preferably equal to or higher than the melting point of the thermoplastic resin, for example, preferably 130 to 220 ° C., more preferably 150 to 215 ° C., and preferably 180 to 210 ° C. More preferable.

  The time for the kneading treatment is preferably 1 to 180 minutes, more preferably 2 to 80 minutes, and particularly preferably 3 to 20 minutes.

  The kneader may be, for example, a kneader, a multi-axial kneader or a multi-axial kneader, a mixing roll, a kneader, a roll mill, a Banbury mixer, a Henschel mixer, a screw press, a disperser, etc. (like a pressure reduction kneader It is possible to select and use one or two or more kinds from among the devices that can shorten the drying time.

<Molding method>
The said thermoplastic resin composition can be shape | molded by a conventionally well-known method, and a high-strength molded object can be obtained. The size, thickness, shape and the like of the molded body are not particularly limited, and may be, for example, sheet-like, pellet-like, powder-like, fibrous or the like.

  In the case of using polypropylene (melting point of about 160 ° C.) as the thermoplastic resin, the temperature at the molding treatment is preferably 160 to 220 ° C., more preferably 170 to 210 ° C., and preferably 175 to 200 ° C. It is particularly preferred to

  As an apparatus for the molding process, for example, one or more of an injection molding machine, a blow molding machine, a hollow molding machine, a blow molding machine, a compression molding machine, an extrusion molding machine, a vacuum molding machine, a pressure molding machine, etc. It can be selected and used.

  The forming process can be performed by a known forming method, and for example, can be performed by mold forming, injection molding, extrusion molding, hollow molding, foam molding and the like. Alternatively, the kneaded product may be spun into a fiber, and mixed with the above-described plant material or the like to form a mat or board. Blending can be carried out by, for example, a method of co-deposition by air lay.

  In addition, this shaping | molding process may be performed continuously with the kneading process of the said process (D). In addition, the thermoplastic resin composition obtained by kneading is once cooled, chipped using a crusher, etc., and then this chip is introduced into a molding machine such as an extrusion molding machine or an injection molding machine. You can also.

The present invention will be described in more detail based on the following examples, but the present invention is not limited to these examples.
Various measurements and evaluations were performed by the following methods.

(Freeness)
It measured based on JISP8121-2: 2012.

(Particle diameter of plant fiber (D50))
The volume-based particle size distribution was measured using a water dispersion of plant fibers, and the median diameter (D50) was determined as the particle size of plant fibers.

(Particle diameter of mixture containing plant fiber and binding agent (D50))
The volume based particle size distribution was measured using the aqueous dispersion of the mixture, and the median diameter (D50) was measured as the particle size of the mixture.

(Bending strength and flexural modulus)
It measured based on JISK7171: 2008 (plastics-how to obtain | require the bending characteristic).

Example 1
(Production of paper sheet: Process (A))
Softwood bleached kraft pulp (NBKP) was adjusted to a Canadian standard freeness of 640 mL with a double disc refiner to make a vegetable fiber. Based on 100 parts by mass of this vegetable fiber, 36 parts by mass of Sumires resin AC (Sumitomo Chemical, existence, concentration 8%) which is melamine-formaldehyde resin, 4 parts by mass of sulfate band (existence, concentration 27%), anionic A raw material slurry was prepared by adding 2 parts by mass of polyacrylamide Heramide F15 (Halima Chemicals, available form, concentration 15%).

Then, the above-mentioned raw material slurry was made into a paper through a wire part, a press part and a drier part to obtain a paper sheet. The drying temperature in this dryer part was adjusted to 110 ° C. In the wire part, a sheet with a basis weight of 150 g / m ² was made using a slanted short mesh in the press part, a straight through type in the press part, and a Yankee drier in the dryer part.

(Crushing of paper sheet: Process (B))
The above-mentioned paper sheet was ground by a cutter mill to obtain mixture particles (D50: 90 μm, bulk density: 120 g / m ³ ). In addition, the particle diameter (D50) of the vegetable fiber in mixture particle was also 90 micrometers.

(Addition of Mixture Particles to Thermoplastic Resin and Kneading: Steps (C) and (D))
10 parts by mass of the mixture particles, 5 parts by mass of maleic acid-modified polypropylene powder (Kayaburi manufactured by Kayaku Akzo) as a compatibilizer, and polypropylene powder (Novatec PP injection molding grade M3, particles manufactured by Nippon Polypropylene) as a thermoplastic resin 85 parts by mass of a diameter of about 500 μm and a melting point of 158 ° C. were stirred in a 500 ml beaker to carry out mixing treatment. The mixed powder was kneaded at 45 rpm with a twin-screw kneader adjusted to 180 ° C. to obtain a thermoplastic resin composition of Example 1. The obtained thermoplastic resin composition was cut into a cylindrical shape of 2 mm in diameter and 2 mm in length by a pelleter to obtain thermoplastic resin composition pellets.

(Forming process)
The thermoplastic resin composition pellets were injection-molded at 180 ° C. into rectangular parallelepiped test pieces (length 59 mm, width 9.6 mm, thickness 3.8 mm).

Example 2
The same procedure as in Example 1 was carried out except that 50 parts by mass, 5 parts by mass and 45 parts by mass of the mixture particles, the compatibilizer and the thermoplastic resin were mixed.

[Example 3]
The same procedure as in Example 1 was carried out except that the above-mentioned melamine-formaldehyde resin was changed to a polyamidoamine epichlorohydrin resin.

Comparative Example 1
The same procedure as in Example 1 was carried out except that particles (bulk density: 60 g / m ³ ) obtained by grinding LBKP pulp for 5 minutes at 2000 rpm with a household juicer mixer were used instead of mixture particles.

Comparative Example 2
The same procedure as in Example 1 was carried out except that cellulose fine particles (D50: 200 μm) manufactured by Rettmeier were used instead of mixture particles.

[Evaluation]
The bending strength and the bending elastic modulus of each of the obtained rectangular parallelepiped test pieces were measured by the method described above. The measurement results are shown in Table 1.

  As shown in Table 1, molded articles molded from the thermoplastic resin compositions of Examples 1 to 3 have high flexural modulus and flexural strength. That is, it turns out that each thermoplastic resin composition of Examples 1-3 can obtain a molded object with high intensity.

  The thermoplastic resin composition of the present invention can be suitably used as a melt-molding material for obtaining a molded article having high strength.

Claims (5)

Containing thermoplastic resin, vegetable fiber and binder,
The thermoplastic resin composition in which the said binder consists of a melamine resin and / or a polyamidoamine resin. The thermoplastic resin comprises one or more combinations selected from polyethylene, polypropylene, polyester, nylon and polyacetal,
The main component of the vegetable fiber is natural cellulose,
The thermoplastic resin composition according to claim 1, wherein a content of the binder with respect to 100 parts by mass of the vegetable fiber is 0.5 parts by mass or more and 20 parts by mass or less. The volume average particle diameter of the vegetable fiber is 5 μm or more and 300 μm or less,
The thermoplastic resin composition according to claim 1 or 2, wherein the binder is a melamine-formaldehyde resin and / or a polyamidoamine epichlorohydrin resin. Providing a mixture comprising plant fibers and a binding agent;
Adding the above mixture to the thermoplastic resin,
The process of preparing the above mixture is
Including the step of mixing plant fibers and a binder, or the step of preparing waste paper pulp derived from waste paper containing a binder,
The method for producing a thermoplastic resin composition according to any one of claims 1 to 3, wherein the binder comprises a melamine resin and / or a polyamide amine resin. Adjusting the volume average particle diameter of the mixture to 5 μm or more and 300 μm or less by physical disintegration treatment of the mixture prior to the adding step;
The process of kneading and processing the thermoplastic resin to which the said mixture was added after the process to add, The manufacturing method of the thermoplastic resin composition of Claim 4.