Cellulose-fiber-dispersing polyolefin resin composite material, pellet and formed body using same, and production method for cellulose-fiber-dispersing polyolefin resin composite material

Abstract

A cellulose-fiber-dispersing polyolefin resin composite material, containing a polyolefin resin containing a polypropylene resin, and a cellulose fiber dispersed in the polyolefin resin, in which a proportion of the cellulose fiber is 1 mass part or more and 70 mass parts or less in a total content of 100 mass parts of the polyolefin resin and the cellulose fiber, and the polyolefin resin satisfies the expression: Mz/Mw≥4, which is a ratio of Z-average molecular weight Mz to weight-average molecular weight Mw to be obtained by a gel permeation chromatography measurement; a pellet or a formed body using this composite material; and a production method for the composite material.

Claims

1. A cellulose-fiber-dispersing polyolefin resin composite material, comprising: a polyolefin resin containing a polypropylene resin; and a cellulose fiber dispersed in the polyolefin resin, wherein a proportion of the cellulose fiber is 5 mass part or more and less than 50 mass parts in a total content of 100 mass parts of the polyolefin resin and the cellulose fiber, wherein the polyolefin resin satisfies the expression: Mz/Mw≥4, which is a ratio of Z-average molecular weight Mz to weight-average molecular weight Mw to be obtained by a gel permeation chromatography measurement, and wherein the weight average molecular weight Mw is in the range of 400,000 or more and 1,000,000 or less.

2. A cellulose-fiber-dispersing polyolefin resin composite material, comprising: a polyolefin resin containing a polypropylene resin; and a cellulose fiber dispersed in the polyolefin resin, wherein a proportion of the cellulose fiber is 5 mass part or more and less than 50 mass parts in a total content of 100 mass parts of the polyolefin resin and the cellulose fiber, wherein the polyolefin resin satisfies the expression: Mz/Mw≥4, which is a ratio of Z-average molecular weight Mz to weight-average molecular weight Mw to be obtained by a gel permeation chromatography measurement, and wherein a melt flow rate (MFR) at a temperature of 230° C. and a load of 5 kgf is 0.05 to 50.0 g/10 min.

3. A cellulose-fiber-dispersing polyolefin resin composite material, comprising: a polyolefin resin containing a polypropylene resin; and a cellulose fiber dispersed in the polyolefin resin, wherein a proportion of the cellulose fiber is 5 mass part or more and less than 50 mass parts in a total content of 100 mass parts of the polyolefin resin and the cellulose fiber, wherein the polyolefin resin satisfies the expression: Mz/Mw≥4, which is a ratio of Z-average molecular weight Mz to weight-average molecular weight Mw to be obtained by a gel permeation chromatography measurement, and comprising aluminum dispersed in the polyolefin resin, wherein a content of the aluminum is 1 mass part or more and 40 mass parts or less based on a total content of 100 mass parts of the polyolefin resin and the cellulose fiber.

4. The cellulose-fiber-dispersing polyolefin resin composite material according to claim 3, wherein a proportion of the number of aluminum having an X-Y maximum length of 1 mm or more in the number of aluminum having an X-Y maximum length of 0.005 mm or more is less than 1%.

5. The cellulose-fiber-dispersing polyolefin resin composite material according to claim 1, comprising a cellulose fiber having a fiber length of 1 mm or more.

6. The cellulose-fiber-dispersing polyolefin resin composite material according to claim 1, wherein a proportion occupied by the polypropylene resin in the polyolefin resin is 50 mass % or more.

7. The cellulose-fiber-dispersing polyolefin resin composite material according to claim 1, wherein the cellulose-fiber-dispersing polyolefin resin composite material comprises an inorganic material, and a content of the inorganic material is 1 mass part or more and 100 mass parts or less based on 100 mass parts of the polyolefin resin.

8. The cellulose-fiber-dispersing polyolefin resin composite material according to claim 1, wherein, in the cellulose-fiber-dispersing polyolefin resin composite material, water absorption ratio after the cellulose-fiber-dispersing polyolefin resin composite material is immersed into water at 23° C. for 20 days is 0.1 to 10%, and impact resistance after the cellulose-fiber-dispersing polyolefin resin composite material is immersed into water at 23° C. for 20 days is higher than impact resistance before the cellulose-fiber-dispersing polyolefin resin composite material is immersed thereinto.

9. The cellulose-fiber-dispersing polyolefin resin composite material according to claim 1, wherein a moisture content is less than 1 mass %.

10. A pellet, which is produced by using the cellulose-fiber-dispersing polyolefin resin composite material according to claim 1.

11. A formed body, which is produced by using the cellulose-fiber-dispersing polyolefin resin composite material according to claim 1.

12. A method for producing the cellulose-fiber-dispersing polyolefin resin composite material according to claim 1, the method comprising any of the following steps (I) to (V); (I) melt-kneading a cellulose-fiber-adhering polyolefin thin film piece in the presence of water, subsequently mixing this melt-kneaded product with a polypropylene resin, and kneading the mixture, with the proviso that, in the cellulose-fiber-adhering polyolefin thin film piece, the amount of the cellulose fiber is smaller than the amount of the polyolefin resin as an average of the dry mass ratio; (II) mixing a cellulose-fiber-adhering polyolefin thin film piece and a polypropylene resin, and melt-kneading the mixture in the presence of water, with the proviso that, in the cellulose-fiber-adhering polyolefin thin film piece, the amount of the cellulose fiber is smaller than the amount of the polyolefin resin as an average of the dry mass ratio; (III) melt-kneading a polyolefin laminated paper and/or a beverage/food pack formed from this polyolefin laminated paper in the presence of water, subsequently mixing this melt-kneaded product with a polypropylene resin, and kneading the mixture; (IV) mixing a polyolefin laminated paper and/or a beverage/food pack formed from this polyolefin laminated paper with a polypropylene resin, and melt-kneading the mixture in the presence of water; and (V) mixing paper with a polypropylene resin, and melt-kneading the mixture in the presence of water; wherein the melt-kneading in the steps (I) to (V) is carried out using a batch type closed kneading device having a stirring blade while satisfying the following condition (i) and/or condition (ii): (i) the highest end-point temperature of melt-kneading is 280° C. or lower; and (ii) the ratio of the Z average molecular weight Mz with respect to the weight average molecular weight Mw of the resulting composite material satisfies the expression: Mz/Mw≥4.

13. The production method for a cellulose-fiber-dispersing polyolefin resin composite material according to claim 12, wherein the cellulose-fiber-adhering polyolefin thin film piece is a polyolefin thin film piece formed by cellulose fibers and aluminum adhering thereto, and the polyolefin laminated paper has an aluminum thin film layer.

14. The production method for a cellulose-fiber-dispersing polyolefin resin composite material according to claim 12, wherein the melt kneading is performed in the presence of water in a subcritical state.

15. The production method for a cellulose-fiber-dispersing polyolefin resin composite material according to claim 12, wherein the cellulose-fiber-dispersing polyolefin resin composite material comprises aluminum dispersed therein, and wherein, in the cellulose-fiber-dispersing polyolefin resin composite material, a proportion of the number of aluminum having an X-Y maximum length of 1 mm or more in the number of aluminum having an X-Y maximum length of 0.005 mm or more is less than 1%.

16. A pellet, which is produced by using the cellulose-fiber-dispersing polyolefin resin composite material according to claim 2.

17. A pellet, which is produced by using the cellulose-fiber-dispersing polyolefin resin composite material according to claim 3.

18. A formed body, which is produced by using the cellulose-fiber-dispersing polyolefin resin composite material according to claim 2.

19. A formed body, which is produced by using the cellulose-fiber-dispersing polyolefin resin composite material according to claim 3.

Description

EXAMPLES

(1) The present invention will be described in more detail based on examples given below, but the invention is not meant to be limited by these.

(2) First, a measuring method and an evaluation method for each indicator in the present invention will be described.

(3) [Shape of Resulting Material (Cellulose-Aluminum-Dispersing Polyolefin Resin Composite Material)]

(4) An appearance of a cellulose-fiber-dispersing polyolefin resin composite material after kneading was evaluated through visual inspection. A material in a state of bulk was deemed as a conformance product (∘); and a material in a powder shape having a particle size of 2 mm or less, or a material which was significantly ignited after kneading was deemed as a nonconformance product (x). The material in the powder shape causes bridging or adhesion to a vessel wall surface for the reason of easily absorbing moisture in air due to small bulk density, and is difficult in charging into a molding machine by self-weight fall upon subsequent molding.

(5) In the present Example, all composite materials obtained by the production method of the present invention fall under the above-described conformance product.

(6) [Impact Resistance]

(7) A test piece (thickness: 4 mm, width: 10 mm, and length: 80 mm) was prepared by injection molding, and Izod impact strength was measured using a notched test piece in accordance with JIS K 7110. A unit of the impact resistance is “kJ/m.sup.2”.

(8) [Impact Resistance after Immersion]

(9) A test piece (thickness: 4 mm, width: 10 mm, and length: 80 mm) was prepared by injection molding. This test piece was immersed in water at 23° C. for 20 days and then taken off, and the surface water was wiped off. Within 3 hours, Izod impact strength was measured using a notched test piece in accordance with JIS K 7110. A unit of the impact resistance is “kJ/m.sup.2”.

(10) [Cellulose Effective Mass Ratio]

(11) A sample (10 mg) formed in a dry state by drying the composite material sample at 80° C. for 1 hour in advance in an ambient atmosphere was used, and based on the results obtained by performing a thermogravimetric analysis (TGA) from 23° C. to 400° C. at a heating rate of +10° C./min under a nitrogen atmosphere, a cellulose effective mass ratio was determined according to the following formula. Measurement was performed 5 times and an average value thereof was determined, and the average value was taken as the cellulose effective mass ratio.
(Cellulose effective mass ratio [%])=(loss of mass [mg] from 270° C. to 390° C. of the composite material sample)×100/(mass [mg] of the composite material sample in a dry state before being provided for the thermogravimetric analysis)
[Water Absorption Ratio]

(12) A composite material which was dried by a hot air dryer at 80° C. in advance until a moisture content was reduced to 0.5 mass % or less was molded into a sheet form having a dimension of 100 mm×100 mm×1 mm by a press to obtain a formed body, and this formed body was immersed into water of 23° C. for 20 days, and based on measured mass values before and after the immersion, water absorption ratio was determined according to the following [Formula A] (in which, upon measuring mass after the immersion, water drops adhered on the surface was wiped off with dry cloth or filter paper.).

(13) With regard to conformance or nonconformance, a case where calculated water absorption ratio satisfies the following evaluation expression [Formula B] was deemed as conformance (∘), and a case where the calculated water absorption ratio does not satisfy the expression was deemed as nonconformance (x).
(Water absorption ratio [%])=(mass after immersion [g]−mass before immersion [g])×100/(mass before immersion [g])  [Formula A]:
(Water absorption ratio)<(cellulose effective mass ratio).sup.2×0.01  [Formula B]:
[Cellulose Fiber Dispersibility]

(14) A composite material which was dried by a hot air dryer at 80° C. in advance until a moisture content was reduced to 0.5 mass % or less was molded into a sheet form having a dimension of 100 mm×100 mm×1 mm by a press to obtain a formed body. This formed body was immersed into water at 80° C. for 20 days, and then a square having a size of 40 mm×40 mm was drawn in an arbitrary place on a surface of the formed body removed from warm water, and further 9 line segments having a length of 40 mm were drawn inside the square at an interval of 4 mm. Roughness on an intermediate line between adjacent two line segments was measured under conditions of cut-off value λc=8.0 mm and λs=25.0 μm by using a surface roughness measuring instrument to obtain 10 lines of roughness curves (specified by JIS B 0601; evaluation length: 40 mm). When the number of mountains having a peak top of 30 μm or more and being convex upward (from the surface toward an outside) was counted in all of 10 lines of the roughness curves, a case where the number of mountains is 20 or more in total was deemed as a nonconformance product (x), and a case where the number of mountains is less than 20 was deemed as a conformance product (∘).

(15) In a case where cellulose fibers are unevenly distributed in a sample, since water absorption occurs locally, and the surface of that portion swells, the number of peaks increases. In a case where cellulose fibers are uniformly dispersed, since the number of peaks reaches a predetermined value or less, dispersibility of cellulose fibers can be evaluated using this method by setting, for example, a predetermined number of peaks of 20 as the threshold.

(16) [Molecular Weight Pattern]

(17) To 16 mg of composite material, 5 mL of a solvent (1,2,4-trichlorobenzene) for GPC measurement was added, and the resulting mixture was stirred at 160° C. to 170° C. for 30 minutes. An insoluble matter was removed by filtration with a metal filter having a pore of 0.5 μm, and GPC was measured on the thus obtained sample (soluble matter) after filtration by using a GPC system (PL220, manufactured by Polymer Laboratories, Inc., model: HT-GPC-2), using, as columns, Shodex HT-G (one) and HT-806M (two), setting a column temperature to 145° C., using 1,2,4-trichlorobenzene as an eluant, at a flow rate of 1.0 mL/min, and injecting 0.2 mL of the sample thereinto. Thus, a molecular weight pattern was obtained by using monodisperse polystyrene (manufactured by Tosoh Corporation), and dibenzyl (manufactured by Tokyo Chemical Industry Co., Ltd.) as standard samples to prepare a calibration curve, and performing data processing by a GPC data processing system (manufactured by TRC).

(18) In the molecular weight pattern obtained by the GPC measurement, Mw is the weight-average molecular weight and Mz is the Z-average molecular weight.

(19) Mw (weight-average molecular weight) and Mz (Z-average molecular weight) are defined by the following formula.
Mw=Σ(Ni−Mi.sup.2)/Σ(Ni.Math.Mi)
Mz=Σ(Ni.Math.Mi.sup.3)/(Ni.Math.Mi.sup.2)

(20) Herein, Mi is the molecular weight and Ni is the number of molecules.

(21) In the molecular weight pattern, a pattern satisfying the following (A) was deemed as a conformance pattern (∘), and a pattern not satisfying the following (A) was deemed as a nonconformance pattern (x).
Mz/Mw≥4  (A)

(22) In addition, in the present Example, in all of the polyolefin resins composing the composite material of the present invention, Mw is in the range of 400,000 to 1,000,000.

(23) [Particle Size Distribution of Aluminum (Judgment of Aluminum Length)]

(24) A composite material was pressed to obtain a 1 mm-thick sheet-form formed body. A proportion (%) of the number of aluminum having an X-Y maximum length of 1 mm or more in the number of aluminum having an X-Y maximum length of 0.005 mm or more was determined by photographing an enlarged photograph of a surface of this formed body by using a microscope, and determining, on aluminum existing in the range of 5.1 mm×4.2 mm, a distribution of X-Y maximum length thereof by using image analysis software. A case where the proportion of aluminum having the X-Y maximum length of 1 mm or more therein is less than 1% was deemed as (∘), and a case other than (∘) was deemed as (Δ). Among the cases of (Δ), a case where aluminum having an X-Y maximum length of 5 mm or more was deemed as (x). As the image analysis software, “Simple image dimension measuring software Pixs2000_Pro” (manufactured by INNOTECH CORPORATION) was used. In addition, an average of the X-Y maximum length was within the range of 0.02 mm to 0.2 mm for all with regard to the materials in which judgment of the aluminum length was deemed as (∘).

(25) [Tensile Strength]

(26) A test piece was prepared by injection molding, and tensile strength was measured on a No. 2 test piece in accordance with JIS K 7113. A unit is “MPa”.

(27) Meanwhile, all of the thus-obtained composite materials shown in Tables 1 to 3 have a moisture content of 1 mass % or less.

Test Example 1

(28) Broken paper of a polyethylene laminated paper (having paper, a polyethylene thin film layer, and an aluminum thin film layer) was pulverized using a rotary blade type pulverizer (manufactured by Horai Co, Ltd.), and this was mixed with polypropylene 1 (BC6, manufactured by Japan Polypropylene Corporation) and water, at the blending ratios shown in Table 1-1. This mixture was charged into a batch type closed kneading device (batch type high-speed agitating device), and the mixture was melt kneaded in the presence of water by performing agitation with a high speed by adjusting a rotating speed of an stirring blade of the device to 40 m/sec in a peripheral speed at a leading edge of the stirring blade, to prepare a cellulose-fiber-dispersing polyolefin resin composite material.

(29) In addition, with regard to an end of kneading, a time point at which a temperature of the material in a device chamber to be measured by a thermometer installed in the batch type kneading device reached the temperature shown in Table 1-2 was taken as the end.

(30) The cellulose effective mass ratio (%) and the content of the polyolefin resin (%) in each composite material determined in the above-mentioned method are shown in the upper part of Table 1-2. Furthermore, the amounts (mass parts) of various components when the total amount of the cellulose fiber and the polyolefin rein was designated as 100 mass parts, which were calculated by the above-described method using the cellulose effective mass ratio (%) and the content (mass %) of the polyolefin resin, are shown in the middle part of Table 1-2. Further, the evaluation results are shown in the bottom part of Table 1-2.

(31) TABLE-US-00001 TABLE 1-1 Comparative Comparative Example 1 Example 2 Example 1 Example 2 Polypropylene 1 70 70 70 70 (mass parts) Broken paper of 30 30 30 30 laminated paper (mass parts) Water (mass parts) 100 100 100 0

(32) TABLE-US-00002 TABLE 1-2 Comparative Comparative Example 1 Example 2 Example 1 Example 2 Cellulose effective mass ratio (%) 14.6 13.9 14.2 — Content of polyolefin resin (mass %) 77.7 78.6 78.0 — Cellulose fiber (mass parts) 15.8 15.0 15.4 — Polyolefin resin (mass parts) 84.2 85.0 84.6 — PP (mass parts) 75.9 75.6 75.9 — PE [resin derived from broken paper 8.3 9.4 8.7 — of laminated paper] (mass parts) Aluminum, ash (mass parts) 8.4 8.1 8.4 — Temperature of material (discharge 180 240 300 — temperature, ° C.) Shape of resulting material ∘ ∘ ∘ x Tensile strength (MPa) 37.7 34.3 29.4 — Impact strength (kJ/m.sup.2) 5.5 5.3 4.6 — Conformance or nonconformance of ∘ ∘ ∘ x aluminum length Cellulose fiber dispersibility ∘ ∘ ∘ x Impact resistance after immersion (kJ/m.sup.2) 9.2 8.3 6.1 — Z-average molecular weight/Weight- 4.6 4.2 3.8 — average molecular weight Molecular weight pattern ∘ ∘ x — Weight-average molecular weight 623000 567000 318000 —

(33) As shown in Table 1-2, when the material temperature increased to 300° C. during melt-kneading, since the molecular weight pattern of the resin composing the resulting composite material did not satisfy the expression “Mz/Mw≥4”, and the high molecular weight component could not be maintained at a predetermined level, this composite material had poor mechanical strength (Comparative Example 1).

(34) Further, when the melt kneading was performed without adding water, any composite material could not be obtained in the form of lumps (Comparative Example 2).

(35) In contrast, when the highest end-point temperature was lowered to a certain extent and melt-kneading was performed in the presence of water, the molecular weight pattern satisfied the expression “Mz/Mw≥4”. As such, with respect to a composite material in which the decrease in the high molecular weight component is suppressed to a predetermined level exhibits, a molded article obtained by injection molding this composite material also had excellent mechanical strength (Examples 1 and 2).

Test Example 2

(36) Without using the broken paper of the polyethylene laminated paper, paper 1 (tray paper), polypropylene 1 and water were blended at the blending ratio shown in Table 2-1. Thus-obtained mixture was charged into a batch type closed kneading device (batch type high-speed agitating device), and the mixture was melt kneaded in the presence of water by performing agitation with a high speed by adjusting a rotating speed of an stirring blade of the device to 40 m/sec in a peripheral speed at a leading edge of the stirring blade, to prepare a cellulose-fiber-dispersing polyolefin resin composite material.

(37) In addition, with regard to an end of kneading, a time point at which a temperature of the material in a device chamber to be measured by a thermometer installed in the batch type kneading device reached the temperature shown in Table 2-2 was taken as the end.

(38) The cellulose effective mass ratio (%) and the content of the polyolefin resin (mass %) in each composite material determined in the above-mentioned method are shown in the upper part of Table 2-2. Furthermore, the amounts (mass parts) of various components when the total amount of the cellulose fiber and the polyolefin rein was designated as 100 mass parts, which were calculated by the above-described method using the cellulose effective mass ratio (%) and the content (%) of the polyolefin resin, are shown in the middle part of Table 2-2. Further, the evaluation results are shown in the bottom part of Table 2-2.

(39) TABLE-US-00003 TABLE 2-1 Comparative Comparative Example 3 Example 4 Example 3 Example 4 Polypropylene 1 70 70 70 70 (mass parts) Paper 1 (mass parts) 30 30 30 30 Water (mass parts) 100 100 100 0

(40) TABLE-US-00004 TABLE 2-2 Comparative Comparative Example 3 Example 4 Example 3 Example 4 Cellulose effective mass ratio (%) 22.8 22.7 22.4 22.5 Content of polyolefin resin (%) 63.5 63.2 63.1 63.6 Cellulose fiber (mass parts) 26.4 26.4 26.2 26.1 Polyolefin resin (mass parts) 73.6 73.6 73.8 73.9 Temperature of material (discharge 180 240 300 — temperature, ° C.) Shape of resulting material ∘ ∘ ∘ x Tensile strength (MPa) 40.5 38.3 32.8 — Water absorption ratio (%) 2.4 2.6 3.9 6.9 Conformance or nonconformance of ∘ ∘ ∘ x water absorption ratio Cellulose fiber dispersibility ∘ ∘ ∘ x Z-average molecular weight/Weight- 4.4 4.3 3.9 — average molecular weight Molecular weight pattern ∘ ∘ x — Weight-average molecular weight 643000 615000 371000 —

(41) As shown in Table 2-2, when the material temperature increased to 300° C. during melt-kneading, since the molecular weight pattern of the resin composing the resulting composite material did not satisfy the expression “Mz/Mw≥4”, and the high molecular weight component could not be maintained at a predetermined level, this composite material had poor mechanical strength (Comparative Example 3).

(42) Further, when the melt kneading was performed without adding water, any composite material could not be obtained in the form of lumps (Comparative Example 4).

(43) In contrast, when the highest end-point temperature was lowered to a certain extent and melt-kneading was performed in the presence of water, the molecular weight pattern satisfied the expression “Mz/Mw≥4”. As such, a composite material in which the decrease in the high molecular weight component is suppressed to a predetermined level exhibits suppressed water absorption ratio, and a molded article obtained by injection molding this composite material also had excellent mechanical strength (Examples 3 and 4).

Test Example 3

(44) Broken paper of a polyethylene laminated paper (having paper, a polyethylene thin film layer, and an aluminum thin film layer) was pulverized using a rotary blade type pulverizer (manufactured by Horai Co, Ltd.), and this was mixed with the above-described polypropylene 1, at the blending ratios shown in Table 3-1. The thus-obtained mixture was charged into the twin screw extruder (TEX30, manufactured by Japan Steel Works, Ltd.) to prepare a cellulose-fiber-dispersing polyolefin resin composite material.

(45) The results are shown in Table 3-2.

(46) TABLE-US-00005 TABLE 3-1 Comparative Example 5 Polypropylene 1 (mass parts) 70 Broken paper of laminated paper (mass parts) 30 Water (mass parts) 0

(47) TABLE-US-00006 TABLE 3-2 Comparative Example 5 Cellulose effective mass ratio (%) 15.1 Content of polyolefin resin (%) 77.7 Cellulose fiber (mass parts) 16.3 Polyolefin resin (mass parts) 83.7 Aluminum, ash (mass parts) 7.8 Shape of resulting material ∘ Tensile strength (MPa) 31.2 Conformance or nonconformance of aluminum length Δ Dispersibility x Molecular weight pattern x

(48) As shown in Table 3-2, in a case where melt-kneading was carried out using a twin-screw extruder, a lumpy composite material could be obtained. However, in the composite material, dispersibility of the cellulose fiber did not reach a desired level. Further, since the molecular weight pattern of the resin composing the resulting composite material did not satisfy the expression “Mz/Mw≥4”, and the high molecular weight component could not be maintained at a predetermined level, this composite material also had poor mechanical strength (Comparative Example 5).

(49) Having described our invention as related to the present embodiments, it is our intention that the invention not be limited by any of the details of the description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.