JP2011201966A - Method for manufacturing pulp fiber reinforced resin, and pulp fiber reinforced resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that a countermeasure is performed by a means for squeezing and depositing a liquid after addition of a dilution solution such as an elastomer to a pulp fiber since in a pulp fiber composite PP (polypropylene), air remained in the fibrillated fine fiber of the surface of the pulp fiber is separated at injection molding and is remained on the molded article as a bubble and the designability is outstandingly reduced, on the contrary, reduction of impact strength is brought.SOLUTION: In the method for manufacturing the pulp fiber reinforced resin, after in the state that the pulp fiber is convected/stirred with air, it is mixed while blowing a dispersion containing a low elastic elastomer, the pulp fiber obtained by removing the solvent used for the dispersion is kneaded with the thermoplastic resin to make the composite.

Description

  The present invention relates to a method for producing a composite of pulp fiber and thermoplastic resin (pulp fiber reinforced resin) obtained by defibrating recovered waste paper. More specifically, the present invention relates to a means for improving toughness by mitigating brittleness that increases with the composite of a composite (pulp fiber reinforced resin). The present invention also relates to a pulp fiber reinforced resin of pulp fiber and thermoplastic resin obtained by defibrating recovered waste paper.

  The use of natural materials for the purpose of reducing carbon dioxide emissions and effective use of resources has been promoted, and pulp fibers obtained by grinding recovered paper into fibers for the purpose of reducing the amount of general-purpose PP (polypropylene) used. Means for achieving the object by mixing are attracting attention.

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

  In addition, a lump or pellet produced using a plasticizer or cellulose hydrophobizing agent having a melting point of 200 ° C. or lower that promotes dispersion of plant fibers to facilitate handling of bulky plant fibers and PP (polypropylene) are kneaded. Thus, means for improving the dispersibility in the resin has been proposed (see, for example, Patent Document 2).

  However, the fine fibers formed on the surface of the pulp fiber and partially fibrillated exhibit an action that inhibits the entanglement associated with the mixing of the pulp fiber and the resin, so that the fiber and the resin are directly and firmly bonded. It is difficult to obtain the composite mode provided. As a result, PP (polypropylene) combined with 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 improvement effect of the composite is impaired. . Furthermore, the air between the fine fibers is likely to remain, and is not easily discharged by simple kneading, but is separated in a flow process under high pressure such as injection molding, and remains in the molded product as bubbles to deteriorate the design. There is a problem.

  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. It has been proposed to improve mechanical strength by mixing and integrating (see, for example, Patent Document 3).

  Further, there has been proposed a whitening prevention means that uses a fibrillated fiber surface that has been squeezed and adhered after applying an elastic resin solution and the fibrillated fiber is fixed to the fiber body (for example, 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

  However, according to the above means, in order to prevent the air remaining in the gap formed by the fibrillated fine fibers on the fiber surface from moving to the surface of the resin molded product and causing whitening, the resin solution enters. Integration of pulp fibers and matrix resin is achieved. However, an increase in brittleness associated with this modification promotes an increase in strength and elastic modulus, but on the other hand, the impact strength is greatly reduced.

  In other words, the resin impregnated for the purpose of modifying the pulp fiber surface needs to promote affinity with the matrix resin, so that the same type of resin is used. As a result, the fibrillated fine fibers on the fiber surface converge on the fiber body. Since there is a pseudo single fiber mode, there is a mode in which the load stress tends to concentrate on the interface between the fiber and the resin.

  This invention was made in order to solve the above-mentioned problems. Between fine fibers formed by fibrillating an olefin-based elastomer such as polyisobutylene having excellent compatibility with PP (polypropylene) on the surface portion of a pulp fiber. Pulp fiber reinforced resin that eliminates air (bubbles) and integrates an olefin-based elastomer rich in viscosity at the interface with PP (polypropylene) as a base material to strengthen the composite of PP (polypropylene) and pulp fibers And a pulp fiber reinforced resin.

  In addition, the design of the molded product is improved due to the absence of bubbles at the interface between the pulp fiber and PP, the flowability is improved during molding due to the presence of a low-melting and viscous elastomer on the fiber surface, and stress. Disclosed are a method for producing a pulp fiber reinforced resin and a pulp fiber reinforced resin, which suppresses a decrease in strength, particularly impact strength, associated with the elimination of residual bubbles, which is a starting point of breakage due to load.

  The method for producing a pulp fiber reinforced resin according to the present invention was used for a dispersion liquid after mixing while sequentially spraying an aqueous dispersion containing a surfactant and a low-elastic elastomer in a state where the pulp fiber was convected and stirred together with air. What remove | eliminated the solvent is knead | mixed with a thermoplastic resin, It is characterized by the above-mentioned.

  The method for producing a pulp fiber reinforced resin according to the present invention includes air (bubbles) containing fine fibers obtained by fibrillating a surface portion of an olefin elastomer such as polyisobutylene having excellent compatibility with PP (polypropylene). It can be eliminated, and an olefin-based elastomer rich in viscosity can be integrated at the interface with PP (polypropylene) which is a base material, so that the composite of PP (polypropylene) and pulp fibers can be strengthened.

The figure which shows Embodiment 1, and is a figure (example) which shows the result of having measured the general physical property using the test piece injection-molded based on specific raw material prescription. The figure which shows Embodiment 1 is a figure (comparative example) which shows the result of having measured the general physical property using the test piece injection-molded based on the specific raw material prescription.

Embodiment 1 FIG.
<Overview>
PP (polypropylene) in which pulp fibers are composited is excellent in rigidity and heat resistance, but causes a reduction in impact strength.

  The fine fibers formed on the surface of the pulp fiber and partially fibrillated are easily entangled with the resin, so that the composite is strengthened, but the air entangled with the fine fibers is a flow process under high pressure such as injection molding. It is separated by this and remains as bubbles in the molded product, reducing the effect of compositing.

  The present invention is characterized in that a composite of a pulp fiber and a thermoplastic resin, in which a resin rich in viscosity is held between fibrillated fine fibers in a fluffy state on the fiber surface, is formed.

  By eliminating the residual air retained between the fine fibers and retaining an excessive amount of viscous low molecular weight olefinic elastomer with no bubbles remaining on the surface of the pulp fiber, a buffer portion of sudden stress load It was possible to suppress the decrease in impact strength.

<Means>
After impregnating the pulp fibers with a dilute solution in which a viscous resin is dissolved, the solvent is removed to eliminate air between the fibrillated microfibers on the surface and to remove the microfibers from the pulp fibers. Integrate with the body.

  At this time, the pulp fiber is impregnated with a dilute solution of a surfactant having both hydrophobic and hydrophilic groups to eliminate the air between the fine fibers on the surface, and then the viscous low molecular weight elastomer is dissolved in the solvent. The thin liquid state was made to adhere by overlapping.

  Further, by mixing a surfactant having a hydrophobic group with PP (polypropylene), the affinity with a resin having excellent viscosity was improved.

  The modified fiber by the above means was formed into a composite molding material by kneading with PP (polypropylene).

  The present invention is characterized in that a resin rich in viscosity is held between fibrillated fine fibers in a fluffy state on the surface of the fiber, and an olefin system rich in excess amount of air held between the fine fibers By replacing the elastomeric polyisobutylene with the surface portion of the pulp fiber, a buffer portion with a sudden stress load was formed to suppress the reduction in impact strength.

  In addition, for the purpose of promoting complexation while suppressing the convergence of fibrillated fine fibers on the pulp fiber surface, polyisobutylene having a low molecular weight is wetted with an aqueous solution of a surfactant having both a hydrophilic group and a hydrophobic group. Modification of the pulp fiber is achieved by spraying a dilute aqueous dispersion, and then spraying a dilute aqueous dispersion of polyisobutylene having a high molecular weight in order, and then drying this.

  Finished pulp fiber has a strong composite state of fibrillated fine fiber and polyisobutylene on its surface, and is coated on the fiber so that polyisobutylene of different molecular weight is laminated together. I got the structure.

The pulp fiber subjected to the above treatment was combined with PP (polypropylene) by kneading in a molten state at 160 to 190 ° C. using an extruder or the like, and the extruded composite resin was processed into granules to secure a molding material.
<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 a surfactant with hydrophilic groups with excellent affinity is easily impregnated to ensure that the fiber body has converged, the hydrophobic group with excellent affinity with the resin has a viscosity dispersed in a dilute solution. Excellent elastomer can be coated firmly.

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

<Effect (Inventive step)>
Air (bubbles) containing pulp fibers containing fine fibers fibrillated on the surface of olefin-based elastomers such as polyisobutylene, which have excellent compatibility with PP (polypropylene), are removed, and the interface with PP (polypropylene) as the base material Since the above-mentioned elastomer rich in viscosity is integrated, the composite of PP (polypropylene) and pulp fiber is strengthened.

  In addition, there is no air bubbles at the interface with pulp fiber and PP (polypropylene), so the design of the molded product is improved. The low melting point and high viscosity elastomer intervenes on the fiber surface. In addition, the decrease in strength, particularly impact strength, due to the removal of residual bubbles, which is the starting point of fracture accompanying stress loading, was suppressed.

  Since polyisobutylene is a resin rich in viscosity, it has a buffering action against external stress, so that it can concentrate on the interface between fiber and matrix resin to relieve the stress that causes fracture and improve impact strength. Can do.

  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, the formation of whitening can be suppressed. Further, the affinity between the fine fibers and the polyisobutylene to be applied by spraying the diluted aqueous dispersion is improved, and the pulp fiber surface can be firmly held.

  In addition, since the polyisobutylene having a small molecular weight is sprayed sequentially on the pulp fiber, it is held and integrated into the gap between the fibers of the fine fiber, so that the added impact stress is easily dispersed throughout the fine fiber. Further, peeling between the pulp fiber and the matrix resin hardly occurs, which can contribute to improvement of toughness.

<Composite of pulp fiber and PP (polypropylene) modified by spraying only a low-elastic resin dilute dispersion>
A method for producing a composite resin obtained by kneading a modified pulp fiber and PP (polypropylene) by applying a dilute aqueous dispersion of PIB (polyisobutylene) will be described in detail below.

  First, PIB (polyisobutylene) was dispersed at high temperature in water equipped with a surfactant until it became an emulsion. However, those having a molecular weight of 100K or more are preferably made easy to disperse by reducing the viscosity by swelling or dissolving with a solvent.

  On the other hand, the pulp fiber is selected from recovered paper that does not have residual chemicals that cause discoloration or alteration, such as acid and chlorine, and is sheared by, for example, throwing it into a gap provided between two opposing disks. Use defibrated with force.

  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% with respect to the pulp fiber, and the aqueous solution to be sprayed is preferably the same amount to double the amount of the pulp fiber.

  The surfactant to be used is characterized by having both a hydrophilic group mainly composed of ethylene oxide and a hydrophobic group composed of a linear alkyl group. Hydrophobic PP (polypropylene) and hydrophilic pulp fiber And the affinity between the surfactant and PIB (polyisobutylene) added thereafter can be promoted.

  Next, PIB (polyisobutylene) water-dispersed dilute solution is sprayed in the order of increasing molecular weight under the condition that the wet pulp fibers containing the surfactant aqueous solution float in the mixer. PIB (polyisobutylene) is in a very fine granular form and is uniformly dispersed in water, and has excellent affinity with the surfactant contained in the pulp fiber, so it easily penetrates between the fibrillated fine fibers. be able to. PIB (polyisobutylene) is first sprayed with 0.5 parts of a 2% dilute dispersion of pulp fiber having a molecular weight of 10K to 20K, which is a highly viscous liquid at room temperature, and then 1 to 80K to 200K. .5 parts were sprayed as a 5% dilute solution.

  If an aqueous dispersion of PIB (polyisobutylene) is not sprayed in the form of a mist in this case and it is directly charged, a homogeneous coating cannot be obtained, and an excessively wet state is formed even if it is partially. Thus, since the fine fibers converge on the pulp fiber main body, the short fiber state is formed, and the problem that the effect of improving the strength cannot be obtained sufficiently remains.

  At this time, when it is suggested that the pulp fibers are less likely to float in the mixer and may adhere to the wall surface and fall into a state of obstructing the uniform application of PIB (polyisobutylene), the spraying of each raw material is completed. In this stage, it is preferable to feed dry air into the mixer to promote drying of the pulp fibers.

  Next, the pulp fiber that has been subjected to the above-described treatment and the melted PP (polypropylene) are kneaded. Using an extruder, the resin temperature is uniformly mixed at a temperature not exceeding 190 ° C., preferably not exceeding 180 ° C. PP (polypropylene) having a low viscosity is applied in consideration of fluidity at the time of injection molding in a composite state with pulp fibers. In this example, MI (fluidity) of 40 g / 10 min is selected, and PIB (polyisobutylene) applied to the pulp fiber surface together with stable extrusion during kneading does not excessively elute into PP (polypropylene). In order to secure a kneading state that allows it to remain moderately, pulp fibers were added so as to have a content of 33 wt% in an initial state where PP (polypropylene) starts melting.

  PP (polypropylene) and pulp fibers that have been kneaded are combined, and the strand discharged from the extruder absorbs moisture by cooling in water and foams at the time of molding. Therefore, it is preferable to perform air cooling and solidification, and appropriately cut this into pellets.

  As a comparative example, various physical properties were evaluated using a test piece obtained from a molding material compounded with PP (polypropylene) by the same means as a pulp fiber not subjected to surface modification.

  Below, the result of having measured the general physical property using the test piece injection-molded based on specific raw material prescription is shown in FIG. 1, FIG. Each example shown here will be described in detail. In Example 1-1, low molecular weight, and in Example 1-2, high molecular weight PIB (polyisobutylene) was added in an amount of 0.8 wt%. In Example 1-3, 0.2 wt. Of each was applied sequentially from the smallest molecular weight, and in Example 1-4, high molecular weight PIB (polyisobutylene) was added to the addition shown in Example 1-3. 0.5 wt% is applied excessively.

  On the other hand, each comparative example will be described in detail. Comparative example 1-1 is blended with low molecular weight, and comparative example 1-2 is blended with PIB (polyisobutylene) having an excessively high molecular weight at an addition amount of 0.8 wt%. Comparative Example 1-3 was obtained by applying 0.3 wt. To Comparative Example 1-3. Comparative Example 1-4 was 0.5 wt.% Of low molecular weight PIB (polyisobutylene) with respect to the addition shown in Comparative Example 1-3. % Is applied in excess.

  In any of the test pieces, compared with PP (polypropylene) combined with pulp fibers not coated with PIB (polyisobutylene), almost no whitening due to residual bubbles is observed, and the surface design is clearly improved.

  Among them, the pulp fiber composite PP (polypropylene) obtained by the present invention is such that the application condition of PIB (polyisobutylene) is held between the fibrillated fine fibers on the surface of the pulp fiber. Compared to those treated under conditions that did not satisfy the conditions, the surface design, strength and elastic modulus, fluidity were excellent, and the improvement in brittleness was confirmed from the impact resistance results.

  That is, in the PP (polypropylene) composite of the present invention applied so that it does not converge on the fiber body even when the fine fibers are combined with PP (polypropylene), the MI (fluidity) is not affected by the form of the combined fibers. ), Thermal deformation temperature, elastic modulus and the like are not different, but the above-mentioned aspect of the fine fiber in PP (polypropylene) makes it difficult to pull out the fiber and makes it easy to restrain deformation of PP (polypropylene). It was confirmed that the PP (polypropylene) composite according to the present invention had significantly higher strength and heat distortion temperature than the comparative example.

Claims (9)

  The pulp fiber is mixed with the aqueous dispersion containing the surfactant and low-elastic elastomer while being convected and stirred together with air, and then mixed, and then the solvent used in the dispersion is removed and kneaded with the thermoplastic resin. And producing a pulp fiber reinforced resin characterized by being combined.   The method for producing a pulp fiber reinforced resin according to claim 1, wherein the pulp fiber is impregnated with a dilute surfactant solution and is in a wet state.   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 different molecular weights of 10K to 200K.   The dispersion containing the low elastic elastomer is dispersed in water using a surfactant having both a hydrophilic group mainly composed of ethylene oxide and a hydrophobic group composed of a linear alkyl group. Item 2. A method for producing a pulp fiber reinforced resin according to Item 1.   The method for producing a pulp fiber reinforced resin according to claim 1, wherein the dispersion containing the low-elastic elastomer is sprayed on the pulp fibers in order from the one having a low molecular weight.   A pulp fiber reinforced resin comprising a pulp fiber provided with a surfactant coated with a low-elastic elastomer and composited with a thermoplastic resin.   The pulp fiber reinforced resin according to claim 6, wherein the surfactant has both a hydrophilic group mainly composed of ethylene oxide and a hydrophobic group composed of a linear alkyl group.   The pulp fiber reinforced resin according to claim 6, wherein the low-elastic elastomer is formed by attaching polyisobutylene having different molecular weights of 10K to 200K to pulp fibers in order from low molecular weight.   9. The pulp fiber reinforced resin according to claim 8, wherein the polyisobutylene is constituted using a molecular weight of 50K or less.

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