JPH0692508B2 - Long fiber reinforced polyolefin resin composition - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a long fiber reinforced polyolefin resin composition. More specifically, the present invention relates to a pellet-shaped long-fiber-reinforced polyolefin resin composition having uniform dispersion of reinforcing long fibers in a molded article, exhibiting excellent falling weight impact strength, and having very little anisotropy of strength and warp deformation.

[0002]

2. Description of the Related Art Fiber-reinforced thermoplastic resins obtained by reinforcing thermoplastic resins such as polyolefin resins with relatively short fibers (generally 3 mm or less) have excellent mechanical strength and rigidity such as tensile strength. It is suitable for use in various industrial parts. However, since such a fiber-reinforced thermoplastic resin is usually produced by melt-kneading the resin and the reinforcing fiber, there is a problem that the fiber is broken into shorter pieces at the time of producing the composition. Therefore, it has a serious drawback that it is inferior in impact strength such as Izod impact strength and falling weight impact strength due to the short length of the fiber, and the anisotropy of the strength and warp deformation depending on the shape of the molded product due to the orientation of the fiber during molding. There is also the problem of causing
At present, its use is limited.

As an improved impact strength of such a fiber reinforced thermoplastic resin, a polyolefin resin is obtained by dry blending 5 to 60 wt% of glass long fibers having a fiber length of 5 to 50 mm, or dry blending and then melt kneading. A composition for heat compression molding has been proposed (JP-A-60-
86139). This composition is a very useful material that is excellent in mechanical strength and rigidity, and also excellent in Izod impact strength. However, examination of this composition revealed the following problems. That is, when this composition is a dry blend product, the openability of the glass fiber during molding is insufficient and the uniform dispersion of the glass fiber in the molded product is poor, and the composition is melt-kneaded. In the case of a product, it means that the glass fibers are broken to a considerable extent during the melt-kneading. Therefore, it was found that almost no improvement was observed in falling weight impact strength, strength anisotropy, and warp deformability in any of the manufacturing methods. Moreover, the molding method of this composition is limited to thermocompression molding,
Although it can be applied to various molding methods by pelletizing after melt-kneading, it was found that the breakage of the fiber becomes more remarkable.

[0004] In addition, as a modified fiber-reinforced thermoplastic resin having improved impact strength, a roving of reinforcing fiber such as glass fiber or carbon fiber is used, which is impregnated with resin and then pultruded to obtain a desired length. A pellet-shaped long-fiber-reinforced thermoplastic resin composition produced by cutting into pieces is known. This composition has extremely long fibers in spite of being in the form of pellets, that is, it has a reinforcing fiber of a length equal to the length of the pellet, and since it is in the form of pellets, it has a screw injection mechanism and a general injection molding machine. It is possible to use a molding machine such as an extrusion molding machine for molding. For example, 30vo for thermoplastic resin with specific viscosity
l% (for polyolefin resin, approximately 50-55wt
A pellet-shaped long-fiber-reinforced thermoplastic resin composition having a length of 2 to 100 mm and containing reinforcing fibers parallel to each other has been proposed (Japanese Patent Laid-Open No. 63-37694). In addition to being excellent in mechanical strength and rigidity, the impact strength is not only excellent in Izod impact strength but also in falling weight impact strength, and the strength anisotropy is also improved, which is extremely useful.

However, the pellet-shaped long fiber reinforced thermoplastic resin as described above has the following problems. That is, the fiber openability at the time of molding is insufficient and the fibers are not uniformly dispersed in the molded article, and
This means that the reinforcing fibers, which are held for a long time in the pellets, will be significantly broken during plasticization by the screw during molding. Therefore, compared to a resin composition reinforced with short fibers, mechanical strength and rigidity, and impact strength such as Izod impact strength is improved, but it is still hard to say that it is at a satisfactory level. The effect of improving strength anisotropy due to fiber orientation and warp deformability is poor.

A diameter of 6 mm is used as a method for preventing the breakage of fibers when injection molding a pellet-shaped long fiber reinforced thermoplastic resin.
The above nozzle, and the groove depth of 5 mm or more, the compression ratio is 1.
Using an injection molding machine having 8 or less screws, screw rotation speed 20 to 50 rpm, injection speed 0.2 to 1.0 m
A method of molding under the condition of / min has been proposed (JP-A-2-292008, JP-A-2-29200).
9). According to this method, it is possible to prevent the fibers from breaking during molding, and the mechanical strength, rigidity, and Izod impact strength are improved. However, when a molded product obtained by this method was examined, it was found that the fiber disintegration was sacrificed as a result of preventing breakage of the fiber, and the uniform dispersibility of the fiber in the molded product was further deteriorated.
For this reason, although there is no particular problem in molding small test pieces, etc., when molding plate-shaped molded products, only falling weight impact strength, strength anisotropy, and warp deformability are unsatisfactory. Not obtained, and this method naturally has its limits.

[0007]

As described above,
The openability of the fiber during molding is sufficiently good, it has excellent mechanical strength and rigidity, and it is excellent not only in Izod impact strength but also in impact strength such as falling weight impact strength. Although long-fiber-reinforced thermoplastic resin compositions with almost no warpage and deformation have been desired as various industrial materials, they have not yet been sufficiently satisfactory. Therefore, an object of the present invention is to provide a pellet-shaped long fiber reinforced thermoplastic resin composition having excellent properties as described above.

[0008]

Means for Solving the Problems The inventors of the present invention, as a result of earnest research on a composition of a polyolefin resin, have found that a polyolefin resin having a melt flow rate of 30 g / 10 min or more and a reinforcing fiber having a fiber length of 5 mm or more. 20 wt
The present invention has been found to be effective in achieving the object of the present invention, and has reached the present invention.

That is, according to the present invention, a polyolefin resin having a melt float rate of 30 g / 10 min or more contains 20 wt% or more of reinforcing long fibers having a fiber length of 5 mm or more and arranged substantially parallel to each other, and , In the cross section of the pellet perpendicular to the direction of the reinforcing filaments
(5d) ² A pellet-shaped long-fiber-reinforced polyolefin resin composition characterized in that the number n of reinforcing fibers contained in a unit circle having an area of (d: average fiber diameter of reinforcing long fibers) satisfies the following formula: ,,.

[Equation 2]

The polyolefin resin used in the present invention includes low density polyethylene, cotton-like low density polyethylene, high density polyethylene, polypropylene, polybutene-1, polypentene-1, polyhexene-1, poly-4-methylpentene-1 and the like. Or a copolymer obtained from a plurality of olefin monomers selected from ethylene, propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1 and the like. Of these, polypropylene or a crystalline copolymer of propylene containing propylene as a main component with ethylene or another olefin is preferable. Further, modified polyolefin resins obtained by graft-reacting these polyolefin resins with unsaturated carboxylic acids or their anhydrides, or
It may be a mixture of a polyolefin resin and this modified polyolefin resin.

The polyolefin resin used in the present invention is 2
It is necessary that the mel flow rate (MFR) (g / 10 min) measured under the conditions of 30 ° C. and 2.16 kg load is 30 or more, preferably 50 or more. When the MFR is less than 30, it is difficult to obtain a composition having good impregnating ability, and when good impregnating ability cannot be obtained, even if it is obtained, the fiber opening property at the time of molding is poor, so that the molded article is The dispersion of the fibers becomes uneven, and the falling weight impact strength, strength anisotropy, and warp deformation are not improved.

As the strength fiber used in the present invention, widely known ones such as glass fiber, carbon fiber, metal fiber, potassium titanate fiber and polymer fiber can be exemplified. These may be used alone or in combination of two or more, and among them, glass fiber is preferable because it has an excellent reinforcing effect. The fiber length of the reinforcing fiber in the present invention must be 5 mm or more, preferably 8 mm or more. If the thickness is less than 5 mm, the effects of improving the impact strength such as Izod impact strength and falling weight impact strength, the anisotropy of strength, and the warp deformability are poor, and therefore should be avoided. Further, the content of the reinforcing fiber needs to be 20 wt% or more. If the content is less than 20 wt%, mechanical strength such as tensile strength,
It should be avoided because it is poor in rigidity and impact strength improving effects such as Izod impact strength and falling weight impact strength.

As a method for producing the composition of the present invention, a method of impregnating a roving type reinforcing fiber with a polyolefin resin, followed by pultrusion and then cutting to a length of 5 mm or more is preferable. There is no particular limitation on the method of impregnating with the polyolefin resin, and the roving is passed through a resin powder fluidized bed and then heated above the melting point of the resin (Japanese Patent Publication No. 52-3985), and roving is performed using a crosshead die. A method of impregnating with a molten polyolefin resin (Japanese Patent Laid-Open Nos. 62-60625 and 63-1320).
36, JP-A-63-264326, JP-A-1-2081
18), a method in which polyolefin resin fibers are used, and this and reinforcing fiber rovings are simultaneously bundled and then heated above the melting point of the resin (Japanese Patent Laid-Open No. 61-118235).

The present inventors have found that the impregnating property of the reinforcing fibers in the pellets with the resin is closely related to the uniform dispersibility of the fibers in the molded article and the falling weight impact strength. That is, in order to achieve the object of the present invention, the pellets must have good impregnation properties, and π · (5d) in the cross section of the pellets orthogonal to the direction of the reinforcing fibers.
² The number n of reinforcing fibers contained in a unit circle having an area of [d: average fiber diameter of reinforcing long fibers] must satisfy the following formula.

[Equation 3]

The term "good impregnation property" as used in the present invention means that the resin penetrates into almost all the fibers constituting the roving and the fibers are present in a monofilament or a state close to the monofilament, and the deviation of the fibers in the pellet is extremely small. Is the state of being. The above formula regulates the degree of deviation of this fiber, and the number n of fibers must not aggregate in one place beyond a certain level (value on the right side of the formula) determined by its content. Indicates. Therefore, n may be partially 0, but n
The maximum value of must satisfy the formula. When the expression is not satisfied, the dispersion of the fibers in the molded product becomes non-uniform, and the falling weight impact strength, the anisotropy of strength, and the warp deformability are not improved.

As a means for achieving a good impregnation property, the roving is squeezed by a metal bar or the like while passing through the fluidized bed of the resin powder, and dispersed in a state close to a monofilament so that the resin powder is easily attached ( Japanese Patent Publication 52-398
5) Roving the metal bar or barrier area provided in the crosshead die to force the molten resin to penetrate (Japanese Patent Laid-Open No. 63-264326), and roving with the roll provided in the crosshead die. Press to force the molten resin to penetrate (Japanese Patent Laid-Open No. 63-1320).
36), and the like.

The higher the wettability of the reinforcing fiber with the resin, the better
Although it is disclosed that it is desirable to achieve high rigidity (Japanese Patent Publication No. 63-37694), the wettability referred to here is the expression of the presence or absence of air bubbles only. Moreover, there is no suggestion of any relation between the impregnating property, the uniform dispersion of the fibers in the molded article, and the falling weight impact strength. The composition of the present invention may optionally contain an antioxidant, a stabilizer for ultraviolet absorbers, a crystal nucleating agent, an antistatic agent, a flame retardant, a plasticizer, a lubricant, a pigment and the like.

The composition of the present invention can be molded by using various general molding machines having a screw plasticizing mechanism. The composition of the present invention has good openability of the fiber at the time of molding even when the kneading of the screw is relatively weak. Therefore, it is rather preferable to mold under the condition of weak kneading in order to prevent the fiber from breaking. desirable. That is, it is preferable to avoid using a screw having a high compression ratio and take into consideration molding at a low screw rotation speed.

[0019]

[Examples] The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(1) MFR According to JIS-K-7210, it was measured at 230 ° C. under a load of 2.16 kg.

(2) Impregnating property: Measurement of the number n of fibers in a unit circle: 10 composition pellets were randomly selected, and a thin piece of 100 to 200 μ was cut out in the direction perpendicular to the length direction of each pellet. The cross section of the pellet was photographed with an optical microscope at a magnification of 200 to 400 times. If the fibers were uneven, the part where the fibers were most concentrated was photographed. From the photograph taken, the number n of fibers contained in a unit circle having an area of π · (5d) ² [d: average fiber diameter of reinforcing fiber] was counted. In the case where the cross section of the fiber was divided by the circumference, the portion included in the circle of the fiber cross section was visually read up to one tenth digit. nmax: maximum value of the above-mentioned 10 measured values n (see Table 1) Reinforcing fiber content x: 2 g of pellets were put in a crucible and baked in an electric furnace, and the amount of residual reinforcing fibers was measured to determine the content [ wt%] was calculated. Measurement of Impregnating Property: When nmax satisfies the following formula, the impregnating property is judged to be ◯, and when it does not satisfy it, it is judged to be x, and the calculated values of the formula are also shown in Table 1.

[0022]

[Equation 4]

(3) Uniform Dispersion of Reinforcing Fibers The surface of the flat plate of the molded product was visually observed. Its typical surface is shown in FIGS. When the distribution is very uniform so that unopened fiber bundles are not seen as shown in a of FIG. 1, ◎, and a large number of unopened fiber bundles are seen as in d of FIG. In the case of such a non-uniform dispersion, the one between x, ◎ and x is ◯ (b in FIG. 1) closer to ◎,
The one closer to x was judged in two stages of Δ (c in FIG. 1).

(4) Fiber Length After Molding A flat plate of the molded product is heated in an electric furnace at a temperature rising rate of 2 ° C./min to 600.
The fibers were burned out by heating to 0 ° C., and the remaining fibers were visually observed. When there are few fiber breaks, the fibers that remain long entangle with each other, and the shape of the molded product remains as it is ◎, when the fiber breaks significantly and the shape of the molded product has collapsed Is ×, ◎
Between x and x, ○ is closer to ◎ and △ is closer to x.
It was judged in stages.

(5) Drop weight impact strength: According to ASTM-D-3029 F method. 50 mm x 50 from molded product
mm (thickness 3.0 mm) test pieces were cut out and measured at a constant height. The impactor had a diameter of 12.7 mm, the test piece support had a hole diameter of 38.1 mm, and the test piece was not clamped and was free. Regarding the judgment of breakage, the time when the test piece cracked was regarded as breakage.

(6) Tensile strength According to JIS-K-7113. A 150 mm × 10 mm (thickness 3.0 mm) test piece was cut out from the molded flat plate along two directions perpendicular to each other (expressed as a 0 ° direction and a 90 ° direction) and measured. Of these, the one with higher strength is shown as the 0 degree direction in Tables 1 and 2 below.

(7) Izod impact strength with notch Compliant with JIS-K-7110. From the molded flat plate along two directions that are perpendicular to each other (expressed as 0 degree direction and 90 degree direction)
A JIS No. 2 A test piece was cut out and measured. Of these, the one with higher strength is shown as the 0 degree direction in Tables 1 and 2 below.

(8) Warpage Deformation The molded flat plate is subjected to 7 ° C. in an atmosphere of 23 ° C. and 50% RH after molding.
It was left for 2 hours for conditioning. This flat plate was placed on a surface plate, and the height of the diagonally raised from the surface plate when one corner was pressed by a weight was measured by changing the position, and the maximum value of the one piece was defined as the warp deformation amount.

The following components were used. (A) Polypropylene-1 MFR 0.5 g / 10 min, 100 parts by weight of powdery propylene homopolymer, 0.09 parts by weight of 1,3-bis (t-butylperoxyisopropyl) benzene, 2,6-t-
0.1 part by weight of butyl-p-cresol was dry blended in advance with a Henschel mixer, and this was 200 ° C with a twin screw extruder with a screw diameter of 45 mm and L / D = 30.
50 g / 10 min MFR propylene homopolymer obtained by melt-kneading in (in Tables 1 and 2 below, abbreviated as PP-1)

(B) Polypropylene-2 1,3-bis (t-butylperoxyisopropyl) benzene was obtained in the same manner as in (a) except that the addition amount of 0.13 parts by weight, MFR 100 g / 10 min. A propylene homopolymer (abbreviated as PP-2 in Tables 1 and 2).

(C) Polypropylene-3 MFR 20 g / 10 min obtained in the same manner as in (a) except that the addition amount of 1,3-bis (t-butylperoxyisopropyl) benzene was 0.05 part by weight. A propylene homopolymer (abbreviated as PP-3 in Tables 1 and 2).

(D) Glass fiber A roving glass fiber having a Tex count of 2200 g / km and an average fiber diameter of 16 μ.

Example 1 MFR 50 g / 10 min propylene homopolymer (PP-1) and glass fiber were pultruded using a single screw extruder having a crosshead die to obtain long fiber reinforced polyolefin resin pellets. Manufactured. The crosshead die used had a structure in which a glass fiber roving was squeezed and a metal bar for forcibly permeating the resin was provided between the fibers. Fiber content is 40
The wt% and pellet length were adjusted to 10 mm. The long fiber reinforced polyolefin resin pellets thus obtained were subjected to an impregnating property check and subjected to an injection molding machine to obtain 150 mm × 150 mm × thickness at a cylinder temperature of 250 ° C., a mold temperature of 50 ° C., and a screw rotation speed of 30 rpm. A 0 mm flat plate was formed. The gate was a 3 mmφ center gate. For this flat plate, or for flat plates or test pieces cut out from this flat plate to the specified dimensions,
Uniform dispersion of reinforcing fibers, fiber length after molding, falling weight impact strength, tensile strength (0 degrees, 90 degrees), notched Izod impact strength (0 degrees, 90 degrees), and warp deformation were evaluated. Table 1 shows the above manufacturing conditions, molding conditions, and evaluation results.

Example 2 Long fiber reinforced polyolefin resin pellets were manufactured, molded and variously evaluated in the same manner as in Example 1 except that a propylene homopolymer (PP-2) having MFR of 100 g / 10 min was used. (See Table 1).

Example 3 Long-fiber-reinforced polyolefin resin pellets were produced, molded and evaluated in the same manner as in Example 2 except that the pellet length was set to 7 mm (see Table 1).

Example 4 Long-fiber-reinforced polyolefin resin pellets were manufactured, molded, and evaluated in the same manner as in Example 2 except that the pellet length was 20 mm (see Table 1).

Example 5 Long fiber reinforced polyolefin resin pellets were produced, molded and variously evaluated in the same manner as in Example 2 except that the fiber content was 20 wt% (see Table 1).

Example 6 Long fiber reinforced polyolefin resin pellets were manufactured, molded and variously evaluated in the same manner as in Example 2 except that the fiber content was set to 60% by weight (see Table 1). As described above, from Examples 1 to 6, all of the compositions according to the present invention have a uniform dispersion of fibers in the molded product, little breakage of fibers, and excellent drop weight impact strength, tensile strength, and Izod impact strength. Moreover, it can be seen that almost no anisotropy of tensile strength and Izod impact strength is observed, and warp deformation is extremely small.

Comparative Example 1 Long fiber reinforced polyolefin resin pellets were manufactured, molded and variously evaluated in the same manner as in Example 2 except that propylene homopolymer (PP-3) having MFR of 20 g / 10 min was used. (See Table 2). Since the MFR of the polymer PP-3 is out of the range of the present invention, the impregnating property of the pellets is poor, whereby the dispersion of the fibers in the molded product becomes non-uniform and the falling weight impact strength is not improved, and the tensile strength , Anisotropy of Izod impact strength and warp deformation also occur.

Comparative Example 2 Long fiber reinforced polyolefin resin pellets were manufactured, molded and variously evaluated in the same manner as in Example 2 except that the pellet length was 3 mm (see Table 2). This is an example of the case where the pellet length, that is, the fiber length of the reinforcing fiber is too short, but the dispersion of the fibers in the molded product is uniform, but the falling weight impact strength, the tensile strength, and the Izod impact strength are poor. Also, warp deformation has occurred.

Comparative Example 3 A propylene homopolymer (PP-1) having an MFR of 50 g / 10 min was directly subjected to an injection molding machine. The molding conditions and various evaluations were performed in the same manner as in Example 2 (see Table 2). This is an example of a polyolefin resin containing no reinforcing fiber, but the falling weight impact strength, the tensile strength, and the Izod impact strength have not been improved at all.

Comparative Example 4 Long fiber reinforced polyolefin resin pellets were manufactured, molded and evaluated in the same manner as in Example 2 except that the fiber content was set to 10 wt% (see Table 2). Although the dispersion of the fibers in the molded product is uniform, the content thereof is so small that the falling weight impact strength, the tensile strength, and the Izod impact strength are not sufficiently improved.

(Comparative Example 5) Production, molding and various production of long fiber reinforced polyolefin resin pellets were carried out in the same manner as in Example 2 except that a cross head die having no metal bar for squeezing glass fiber roving was used. The evaluation was performed (see Table 2). Since the impregnating property of pellets is poor,
Since the dispersion of fibers during molding is not uniform, drop impact strength is not improved, and anisotropy of tensile strength and Izod impact strength and warpage modification occur.

(Comparative Example 6) The pellets obtained in Comparative Example 5 having poor impregnability were used, and the screw rotation speed was 50 rp for the purpose of making the dispersion of the fibers in the molded product as uniform as possible.
Molding was carried out by increasing m, but the uniform dispersibility was not improved (see Table 2).

(Comparative Example 7) The pellets obtained in Comparative Example 5 having poor impregnability were used, and the screw rotation speed was 200 rpm.
However, not only was the achievement of uniform dispersion unsatisfactory, but the fibers also became more prominent, resulting in lower drop weight impact strength, tensile strength, and Izod impact strength, as well as anisotropy and warpage. The deformation was also not improved (see Table 2).

[0046]

[Table 1]

[Table 2]

[0047]

EFFECTS OF THE INVENTION The long-fiber-reinforced polyolefin resin composition of the present invention has the MFR of the polyolefin resin and the impregnating property of the resin with respect to the reinforcing fibers in the pellets so that the fiber openability during molding is improved. It was extremely good. Also, in combination with the specification of the fiber length and content of the reinforcing fiber, by molding under the condition of relatively weak kneading, the dispersion of the fiber in the molded product is uniform and there is little breakage, and the mechanical strength such as tensile strength. In addition to excellent mechanical strength and rigidity, it is also possible to obtain molded products with excellent impact strength such as Izod impact strength and falling weight impact strength, and with almost no anisotropy of strength or warpage deformation. Therefore, the composition of the present invention can be suitably used for various industrial parts, particularly structural parts.

[Brief description of drawings]

FIG. 1 is a diagram showing a dispersed state of glass fibers on the surface of a flat plate of a molded product.

[Explanation of Codes] a Surface of molded article having the best dispersion of glass fibers judged as ⊚ Surface of molded article having good dispersion of glass fibers judged as o ○ Dispersion of glass fibers judged as Δ is slightly poor Surface of molded product Surface of molded product with poor dispersion of glass fiber judged as d x

Claims (1)

[Claims] 1. A reinforcing resin having a melflow rate of 30 g / 10 min or more and 20 wt% of reinforcing long fibers having a fiber length of 5 mm or more and arranged substantially parallel to each other.
% Or more and a reinforcing fiber contained in a unit circle having an area of π · (5d) ² (d: average fiber diameter of the reinforcing long fiber) in a cross section of the pellet orthogonal to the direction of the reinforcing long fiber. The number n of the above satisfies the following formula: Pellet-form long fiber reinforced polyolefin resin composition. [Equation 1]