JP2012102162A - Method for producing pulp fiber reinforced resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problem: pulp fiber composite PP remarkably deteriorates designability because air remaining on pulp fiber surfaces and among fibers separates under a high pressure applied during injection molding and remains as bubbles in a molded article, and in order to prevent the deterioration, the residual air is removed by impregnating a dilute solution of an elastomer or the like into pulp fibers by immersion in the solution and then squeezing the pulp fibers, however, this method brings reduction of impact strength.SOLUTION: A method for producing a pulp fiber reinforced resin is characterized in that a surfactant is applied to cotton-like pulp fibers in a suspended state after defibration by stirring in a mixer; an aqueous dispersion of a low elastic elastomer dispersed in water with a surfactant of the same kind or the same stock as the above surfactant is sprayed; and using a mixture obtained by adhering fine particles of a thermoplastic resin put thereafter to the long pulp fiber surfaces, melt kneading and composite formation are carried out.

Description

  The present invention relates to a pulp fiber reinforced resin, which is a composite of pulp and a thermoplastic resin containing pulp fibers obtained by defibrating recovered recovered paper, etc., and to reduce toughness by mitigating brittleness that increases with compounding. The present invention relates to a method for producing a pulp fiber reinforced resin to be improved.

  Means for mixing pulp fibers obtained by pulverizing recovered paper into fibers for the purpose of reducing the amount of synthetic resin used by combining with natural materials to reduce carbon dioxide emissions and effectively use resources There is.

  For example, there has been proposed a means for melt-mixing a composite of pulp fibers with a mixture of defibrated waste paper obtained by pulverization and PP (polypropylene) (see, for example, Patent Document 1).

  Further, in order to facilitate handling of bulky plant fibers, PP (polypropylene) is used with a lump or pellet in a state that can promote the dispersion of plant fibers using a plasticizer or cellulose hydrophobizing agent having a melting point of 200 ° C. or lower. Means for improving dispersibility in a resin by kneading have been proposed (see, for example, Patent Document 2).

  However, the fine fibers formed on the surface of the pulp fiber and partially fibrillated easily form a form in which the pulp fibers are intertwined with each other and are defibrated by the shearing force received during mixing with the resin. No good dispersion state can be obtained. As a result, PP (polypropylene) containing pulp fibers is excellent in rigidity and heat resistance, but on the other hand, brittleness such as reduction in impact strength and tensile elongation is increased, and the effect of improving the composite is impaired.

  Further, the air between the fine fibers is not easily discharged in the kneading process, but remains in the molding material, and is separated in the flow process under high pressure such as injection molding, and the whitened portion remaining as fine bubbles in the molded product is removed. Since it forms, the designability falls.

  In order to solve this problem, as a means for coating the surface of the pulp fiber with a resin which is a matrix after coating the fiber surface by spraying in a liquid state in which an olefin-based thermoplastic resin is dispersed in a solvent, etc. Means for improving mechanical strength by mixing and integrating have been proposed (see, for example, Patent Document 3).

  In addition, a means for preventing whitening has been proposed by using the fibrillated fiber to fix the fibrillated fiber to the fiber body by attaching the elastic resin solution to the fibrillated fiber surface and then attaching it to the fiber body. (For example, see Patent Document 4).

JP 05-320367 A Japanese Patent Application Laid-Open No. 06-073231 Japanese Patent Laid-Open No. 08-020021 JP 09-228250 A Japanese Patent Laid-Open No. 11-5203 JP 2003-169978 A JP 08-252557 A

  In order to prevent whitening caused by the air remaining in the fibers moving to the surface of the resin molded product, these means achieve the integration of the pulp fibers and the resin forming the matrix by the penetration of the resin solution, and the remaining air Eliminate the problem. However, according to this modification method, it is difficult to impregnate the resin solution up to the gap formed by the fibrillated fine fibers on the surface when the fibers are intertwined to form an aggregated state. However, the increase in brittleness leads to an increase in strength and elastic modulus, but on the other hand, impact strength is greatly reduced.

  In other words, because the resin impregnated for the purpose of modifying the pulp fiber surface needs to promote affinity with the matrix resin, it is necessary to use a similar resin, so it does not lead to filling the gap of fine fibers held on the fiber surface However, the load stress concentrates on the remaining bubbles and leaves a mode that breaks easily from the interface between the pulp fiber and the resin, and the reinforcing effect of the pulp fiber cannot be obtained. There was a problem of inviting a decline.

  The present invention has been made to solve the above-described problems, and suppresses the aggregation of fibers, imparts excellent dispersibility to the pulp fiber in the composite resin, and the elastomer is the pulp fiber. Provided is a method for producing a pulp fiber reinforced resin that can be applied to a surface to form a buffer portion of a sudden stress load and suppress a reduction in impact strength due to the composite.

  In the method for producing a pulp fiber reinforced resin according to the present invention, a surfactant is applied to a pulp fiber having a cotton-like shape after applying a surfactant in a state of obtaining a floating state after defibrillation by stirring in a mixer. Sprayed with an aqueous dispersion of a low-elastic elastomer dispersed in water with the same or similar surfactant as in Example 1, and then melt-kneaded using a mixture in which the fine particles of the thermoplastic resin added were adhered to the surface of the pulp long fibers. And composite.

  The method for producing a pulp fiber reinforced resin according to the present invention is obtained by applying a surfactant to a pulp fiber having a cotton-like shape after obtaining a floating state after defibration by stirring in a mixer, Sprayed with an aqueous dispersion of low-elastic elastomer dispersed in water with the same or similar surfactant, and then melt-kneaded using a mixture in which fine particles of the thermoplastic resin added were adhered to the surface of the pulp long fiber. By compounding, the fibers are prevented from aggregating again, imparting excellent dispersibility to the pulp fiber in the compounding with the resin, and the elastomer is applied to the surface of the pulp fiber rapidly. Since a buffer portion with a sufficient stress load is formed, it is possible to suppress a decrease in impact strength due to the combination.

The figure which shows Embodiment 1 and is a figure which shows the result of having measured the general physical property using the test piece which injection-molded PP (polypropylene) compounded with the pulp fiber as a molding material.

Embodiment 1 FIG.
<Overview>
Pulp fibers to be combined with PP (polypropylene) have a great influence on the impact strength depending on the fiber length, but on the other hand, the pulp fibers are provided with fine fibers formed by partially fibrillating and are easily entangled with each other. As a result, fibers are agglomerated with a resin such as PP (polypropylene) to prevent uniform dispersion, and air remaining between the fine fibers of the intertwined fibers cannot be sufficiently eliminated, and injection molding is performed. In addition to causing fine bubbles to separate when flowing under the high pressure of the time and partially whitening the molded product to cause deterioration in design properties, it also suppresses the development of strength.

  The present invention relates to a means for uniformly dispersing long fibers provided with fine fibers fibrillated on the surface so that they are not easily entangled with each other, and by holding the powder of PP (polypropylene) used for the base material on the surface of the pulp fibers, It is characterized in that the mutual entanglement is inhibited to suppress aggregation and the long fibers are uniformly dispersed in the composite resin.

<Means>
In a state where the agglomerated pulp fiber is suspended by obtaining a temporary defibrated state due to the shearing force generated when it collides with the high-speed rotor blade in the mixer, the PIB ( After spraying a dilute aqueous dispersion of polyisobutylene), fine particles of PP (polypropylene) were added and held on the surface of the pulp fiber, thereby preventing the pulp fiber from aggregating again.

  At this time, by spraying a dilute solution of a surfactant having both a hydrophobic group and a hydrophilic group onto the pulp fiber and impregnating it between the fine fibers, by spraying with an aqueous dispersion of PIB (polyisobutylene) rich in adhesiveness, The effect which can exclude the air which exists between the said fine fibers was provided.

  Furthermore, the PP (polypropylene) introduced thereafter is easily adhered to suppress contact between the fibrillated fine fibers on the surface to prevent entanglement, and the composite resin is obtained by melt kneading using an extruder. By promoting uniform dispersion inside, it was possible to improve the design and improve the strength.

<Prior art>
According to Patent Document 3 (Japanese Patent Laid-Open No. 08-020021), the means for coating the surface of the pulp fiber with resin is coated on the fiber surface by spraying it in a liquid state in which an olefin-based thermoplastic resin is dispersed in a solvent. There is an example of improving the mechanical strength by making it.

  Patent Document 4 (Japanese Patent Application Laid-Open No. 09-228250) describes a means for preventing whitening by using a fibrillated fiber surface that has been squeezed and adhered after applying an elastic resin solution. Yes.

  Regarding composites with pulp fibers, Patent Document 1 (Japanese Patent Laid-Open No. 05-320367) introduces a means for melting and mixing a mixture of defibrated waste paper obtained by pulverization and PP.

  Further, in Patent Document 2 (Japanese Patent Application Laid-Open No. 06-073231), a plasticizer or cellulose hydrophobizing agent having a melting point of 200 ° C. or lower is used to knead plant fiber dispersion with PP (polypropylene). Discloses means for improving dispersibility.

  On the other hand, prior art relating to a resin composite of pulp fiber uses a molding material obtained by kneading a thermoplastic resin by adding an adhesive after dry defibration of waste paper raw material to Patent Document 5 (Japanese Patent Laid-Open No. 11-5203) Means for performing heat and pressure molding at a predetermined temperature have been introduced.

  Patent Document 6 (Japanese Patent Application Laid-Open No. 2003-169978) discloses a method for manufacturing a cushion material in which a binder liquid is sprayed onto the surface of a spherical cotton that has been floated by stirring.

  Further, Patent Document 7 (Japanese Patent Laid-Open No. 08-252557) discloses a means for producing a waste paper board by uniformly mixing waste paper pulp and thermoplastic fine fibers before heat treatment.

<Differences from the prior art>
The present invention uses a dilute solution of a surfactant having both a hydrophobic group and a hydrophilic group in order to facilitate the removal of air in the space of the fibrillated fine fiber on the surface of the pulp fiber. After being easily impregnated with a surfactant having a hydrophilic group having excellent affinity, an elastomer having excellent viscosity dispersed in a dilute solution can be firmly coated by the action of a hydrophobic group having excellent affinity with the resin.

  On the other hand, by coating the surface portion with a resin having excellent viscosity, they are integrated with each other by kneading with PP (polypropylene), thereby increasing the buffering effect at the interface portion between the two materials and contributing to the improvement of the impact strength.

  Further, in the formation of a composite of pulp fiber and resin, there is no means for preventing re-aggregation after the fiber is released from the agglomerated state, and the technical features of the present invention are not captured.

<Effect (Inventive step)>
Since an aqueous dispersion of PIB (polyisobutylene) was sprayed on the pulp long fiber after impregnating the surfactant with the pulp long fiber, the air (bubbles) remaining between the fine fibers was eliminated, and PP ( Polypropylene) suppresses the entanglement of the fibers and is uniformly dispersed in the excess PP. As a result, the suppression of whitening caused by the discharge of bubbles during injection molding and the strength of the combined resin are improved. In addition, PIB (polyisobutylene), which has a low melting point and is rich in viscosity, is interposed on the fiber surface, so that the fluidity at the time of molding does not decrease excessively, and even if the rigidity is improved, a sudden stress load can be alleviated. Since it has the characteristics, the impact strength is prevented from decreasing.

  A method for producing a composite resin obtained by kneading pulp fiber modified with a dilute aqueous dispersion of PIB (polyisobutylene) and PP (polypropylene) in a powder state will be described in detail below.

  First, PIB (polyisobutylene), which is a low-elastic elastomer, was dispersed at high speed with high-temperature water containing a surfactant until it became a state of emulsion (emulsified and dispersed in water). The PIB (polyisobutylene) used here is preferably 50K (K means x1000, 50K = 50000, the same applies hereinafter) having adhesiveness, and those having a molecular weight of 100K or more use a solvent. Therefore, it is essential to reduce the viscosity by swelling or dissolving it and then disperse it, so that it is necessary to eliminate the solvent used according to the application of the composite resin. However, those having a temperature of 200K or more are not preferable because they do not provide the adhesiveness required by the present invention.

  For the pulp fiber, a recovered paper that does not contain residual chemicals that promote discoloration or alteration such as acid or chlorine is selected. The selected recovered paper is obtained by defibration by a shearing force, for example, by putting it in a gap provided between disks facing two oppositely rotating disks.

  For the modification of the pulp fiber, a dilute aqueous solution of a surfactant is sprayed in the form of a mist while the pulp fiber is suspended in a mixer equipped with a blade rotating at high speed, such as a Henschel mixer. The amount of the surfactant to be added is preferably 0.5 to 2.0 parts by weight based on 100 parts of the pulp fiber, and the aqueous solution to be sprayed is preferably 1/10 to 1/2 of the pulp fiber.

  The surfactant used preferably has both a hydrophilic group mainly composed of ethylene oxide and a hydrophobic group composed of a linear alkyl group. This can promote the affinity between hydrophobic PP (polypropylene) and hydrophilic pulp fibers, and the affinity between the surfactant and PIB (polyisobutylene) added thereafter.

  Next, a water-dispersed dilute solution of PIB (polyisobutylene) is sprayed in a state where pulp fibers containing an aqueous solution of a surfactant and in a moderately wet state float in the mixer. PIB (polyisobutylene) is in a state in which very fine particles are uniformly dispersed in water, and has excellent affinity with the surfactant contained in the pulp fiber, so that it can easily penetrate between the fibers. The PIB (polyisobutylene) used here was a 5% dilute dispersion having a molecular weight of about 80K exhibiting high adhesiveness at room temperature, and sprayed so that 1.5 parts of pulp fiber was covered.

  If the PIB (polyisobutylene) aqueous dispersion is directly added without spraying, a homogeneous coating state cannot be obtained, and a partly excessively wet state is formed, and this part is the surface of the pulp fiber. Since the fine fibers prepared in the process converge, a short fiber is formed. For this reason, the effect of sufficient strength improvement cannot be obtained.

  In the above-described application of PIB (polyisobutylene) to pulp fibers, when excessively wet, the pulp fibers are less likely to float in the mixer, and PIB (polyisobutylene) continued due to excessive adhesion to the wall surface. It will fall into the state which inhibits uniform application | coating of. When this situation or possibility is suggested, it is preferable to stop spraying of each raw material and to inject dry air into the mixer to promote drying of the pulp fibers.

  Next, PP (polypropylene) powder is added to the pulp fiber that has been subjected to the above treatment, and mixed in the same manner. The addition of the PP (polypropylene) powder is accomplished by continuing the surface treatment by applying PIB (polyisobutylene) to the pulp fiber described above, and adding a predetermined amount. In the mixer, the pulp fibers are maintained in a defibrated state without being agglomerated by shearing force received from blades rotating at high speed. In this state, PP (polypropylene) powder is charged, and stirring is stopped when a state in which both materials are suspended in the air and a uniform mixture is obtained is obtained.

  The PP (polypropylene) powder used here is a low-viscosity powder in consideration of a decrease in fluidity during injection molding due to compounding with pulp fibers. In this embodiment, an MI (melt flow index) of 40 g / 10 min is selected, and the amount of PIB (polyisobutylene) applied to the pulp fiber during melt-kneading is not excessively eluted and remains appropriately. The content of the pulp fiber is 33 wt% so as to suppress loss of fluidity.

  By obtaining a state of staying in the lower part of the agitator tank by stopping the stirring, the PP (polypropylene) powder contacting the pulp fiber covers the fiber surface and is held via PIB (polyisobutylene). Aggregation between each other is suppressed and a mixture that can be handled as a powder fluid is obtained.

  The above mixture, which has obtained the above characteristics of powder fluid and can be continuously charged, was melt kneaded using an extruder. In this case, in order to prevent excessive discoloration of the pulp, the cylinder temperature and the extrusion speed of the extruder are preferably set so that the resin temperature does not exceed 190 ° C., preferably 180 ° C., and then melt kneading is preferably performed.

  A composite of PP (polypropylene) and pulp fiber that has been kneaded, and the strand discharged from the extruder absorbs moisture by cooling in water and foams during molding, causing problems in appearance. Therefore, it is preferable to perform air cooling and solidification, and appropriately cut this into pellets.

  Below, the general physical property was measured using the test piece which injection-molded PP (polypropylene) compounded with the pulp fiber by the above-mentioned means as a molding material.

  FIG. 1 is a diagram showing Embodiment 1, using a test piece obtained by injection molding PP (polypropylene) combined with pulp fibers as a molding material, and using general physical properties (MI, bending strength, bending elastic modulus, impact strength, It is a figure which shows the result of having measured surface appearance.

  As a comparative example that does not depend on the means of the present invention, Comparative Example 1-1 was obtained by applying a mixture of PP (polypropylene) powder using the same mixer after applying only the surface activity to the pulp fiber and melting it with an extruder. A molding material kneaded and pelletized, Comparative Example 1-2 is a molding material obtained by directly mixing pulp fibers and PP (polypropylene) powder, and then melt-kneaded and pelletized using an extruder, each obtained by injection molding. Various physical properties of the test specimens are also shown.

  The pulp fiber composite PP (polypropylene) according to the present embodiment has a flow of PIB (polyisobutylene) that is maintained between the fine fibers on the surface of the pulp fiber, compared with that processed under conditions that do not satisfy the above conditions. Excellent in resistance, impact resistance and surface design. The pulp fiber impregnated with only the surfactant is dispersed in a state of being held in a wet state by a shearing force received in a stirring state by a blade rotating at high speed in a tank of a stirrer together with PP (polypropylene) powder. When PIB (polyisobutylene) held by the fibers during melt-kneading is melted and kneaded prior to PP (polypropylene), the air that is already between the pulp fibers is eliminated to eliminate the air that was already between the fine fibers. No separation or whitening occurs due to the high pressure received in the mold during molding.

  In contrast, the pulp fiber impregnated with only the surfactant without retaining PIB (polyisobutylene) (Comparative Example 1-1) was fast in a stirrer together with PP (polypropylene) powder in a wet state. While dispersion occurs due to the shearing force received by the rotating blades, PIB (polyisobutylene) is not held on the surface, so the air between fibers cannot be sufficiently eliminated during melt-kneading by the extruder, and the inside of the mold during injection molding It is discharged by the high pressure received at, and will be visually recognized as whitening.

  On the other hand, pellets obtained by melt-kneading with an extruder after stirring and mixing with PP (polypropylene) rotated at high speed in a tank of a stirrer without performing a treatment using a surfactant and PIB (polyisobutylene) In the case of (Comparative Example 1-2), the pulp fiber cannot be completely excluded even if it receives the shearing force received during the melt kneading of PP (polypropylene) between the fine fibers and the pulp fibers included in the pulp fiber. As a result, fine bubbles are discharged during the injection flow under high pressure received in the mold during injection molding, and this is the part where the pulp fibers are aggregated on the surface of the molded product, and the whitening of about 0.1 to 3 mm The dots are visible on the surface of the molded product.

  In addition, any test piece that does not contain a surfactant and PIB (polyisobutylene) absorbs impact stress without receiving a buffering action due to the high viscosity of PIB (polyisobutylene) adhering to the surface of the pulp fiber. It becomes easy to be destroyed with the bubbles staying in the starting point, and the impact strength is significantly reduced.

  From this, the means for reinforcing pulp fiber according to the present embodiment is that the obtained pellets are prevented from remaining air in the pulp fiber and have excellent dispersibility as compared with the comparative example. At the same time, since it is not held between the fibers accompanying the aggregation of the fibers, the occurrence of whitening can be suppressed. It was also confirmed that excellent impact strength was developed in response to impact absorption due to the high viscosity of PIB (polyisobutylene).

  In the method for producing a pulp fiber reinforced resin according to the embodiment of the present invention, a pulp fiber is introduced into a mixer having a rotating blade rotating at high speed, and a defibrated state due to a shearing force generated by a collision with the rotating blade is obtained. After that, PIB (polyisobutylene), which is highly adhesive, is sprayed onto the fibrillated fine fibers that are fluffed on the fiber surface, and then the PP (polypropylene) powder that forms the base material is added and mixed and held. It was made to be characterized.

  At this time, after being impregnated by spraying and impregnating a surfactant similar to the surfactant used for water dispersion of PIB (polyisobutylene) with excellent affinity for pulp fibers, a dilute aqueous dispersion of PIB (polyisobutylene) in a wet state Was applied to the gaps and surfaces of the fine fibers on the surface of the pulp fibers.

  The mixture of the pulp fiber and PP (polypropylene) subjected to the above treatment was melt-kneaded at 170 to 190 ° C. using an extruder or the like to form a composite and processed into a granule to secure a molding material.

  In the method for producing a pulp fiber reinforced resin according to the embodiment of the present invention, a mixture of pulp fiber coated with PIB (polyisobutylene) mixed in a mixer and PP (polypropylene) in a powder state is allowed to stand after the standing. Since (polypropylene) is held on the pulp fiber via PIB (polyisobutylene), the pulp fiber does not exhibit an aggregated state. Therefore, when put in an extruder or the like, the PIB (polyisobutylene) melts at a lower temperature than PP (polypropylene) at the time of melt kneading to eliminate the air between the fibers, and then a high shear force is formed, so that the pulp fiber Therefore, the pulp fiber obtained high dispersibility in the composite and improved various strengths.

  In addition, a dilute aqueous solution of a surfactant having both a hydrophobic group and a hydrophilic group was sprayed to impregnate the fine fibers on the fiber surface, so that the fine fibers on the fiber surface were easily impregnated to eliminate air, and the surface of the molded product during injection molding In addition, a dilute aqueous dispersion of PIB (polyisobutylene) using the same or similar surfactant was applied to fine fibers, so that the affinity was improved and the surface of the pulp fibers was improved. The holding could be performed firmly. As a result, in addition to suppressing the occurrence of whitening points on the surface of the obtained molded product, PIB (polyisobutylene) used here is an elastomer rich in viscosity. Therefore, at the interface between pulp fibers and PP (polypropylene). The impact strength can be improved by providing a buffering action of concentrated stress.

Claims (4)

  In the state that the pulp fiber showing flocculent is in a floating state after defibration by stirring in the mixer, after applying the surfactant, disperse it in water with the same or similar surfactant as the surfactant. A low-elastic elastomer aqueous dispersion is sprayed, and then the pulp fiber reinforcement is characterized by melting and kneading using a mixture in which the fine particles of the thermoplastic resin added thereto are adhered to the surface of the pulp long fibers to form a composite Manufacturing method of resin.   The method for producing a pulp fiber reinforced resin according to claim 1, wherein the fine particles of the thermoplastic resin are added excessively than the pulp fibers, and the composite is achieved by melt kneading using the same.   The method for producing a pulp fiber-reinforced resin according to claim 1, wherein the low-elastic elastomer is an aqueous dispersion of polyisobutylene having a molecular weight of 50K to 200K.   The pulp according to claim 1, wherein the low elastic elastomer is water-dispersed using a surfactant mainly composed of ethylene oxide having both a hydrophilic group and a hydrophobic group composed of a linear alkyl group. Manufacturing method of fiber reinforced resin.

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