JPH07100829A - Method for producing long fiber reinforced thermoplastic resin sheet - Google Patents

Abstract

(57) [Summary] [Structure] In the production of a stampable sheet by a lamination method, a reinforcing fiber layer made of a reinforcing fiber mat made of discontinuous long fibers having a length of 50 mm or more is formed by one set or two or more sets of uneven rolls. Open the fiber. The reinforcing fiber layer thus opened is laminated with the resin layer to form a stampable sheet. Continuous fibers may be opened and oriented in one direction and mixed into the reinforcing fiber layer. [Effect] While maintaining the high strength and stability of strength characteristics peculiar to the long fiber reinforced thermoplastic resin sheet, the energy absorption characteristics at the time of breaking are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a long fiber reinforced thermoplastic resin sheet (stampable sheet), and more specifically, a long fiber reinforced thermoplastic resin excellent in energy absorption characteristics at the time of breaking. The present invention relates to a method for producing a sheet by a laminating method.

[0002]

2. Description of the Related Art In recent years, the weight of materials has been reduced in various industrial fields from the viewpoint of energy saving. As a promising means for reducing the weight, it is possible to substitute the metal material with another low specific gravity material, for example, a fiber reinforced resin material. Among them, a sheet of fiber-reinforced thermoplastic resin material that uses a thermoplastic resin as a matrix resin is called a stampable sheet because it can be press-formed (stamping forming) like a steel sheet, and is an integral molding of multiple parts. As a lightweight material with excellent strength characteristics, the demand for it is increasing mainly in the automobile field. Fiber-reinforced thermoplastics are also advantageous in that they can be recycled by reshaping.

Typical methods for producing stampable sheets are roughly classified into a papermaking method and a laminating method. In the papermaking method, resin powder and discontinuous reinforcing fibers (chopped strands) are slurried in water and formed into a sheet by the same method as papermaking,
This is a method of heating and pressurizing to integrate (JP-A-60-1582).
28, JP-A-4-163108, etc.). The sheet obtained by this method has excellent dispersibility of reinforcing fibers and uniform fiber filling properties. However, the papermaking method is disadvantageous in cost because it requires a large amount of water treatment and dehydration / drying steps. Moreover,
Since long fibers with a length of 50 mm or more are difficult to use and the reinforcing fibers are three-dimensionally oriented in the sheet, there are weak points that the tensile strength and impact strength of the sheet are low and the strength characteristics are unstable. .

On the other hand, in the laminating method, continuous fiber layers (eg, strands or rovings) or discontinuous fiber layers (eg, chopped strand mats) and resin layers (resin sheets) are alternately laminated, and heated rolls or This is a method of heating and pressurizing between the belts (JP-A-61-279519, JP-B-59-).
No. 34487, etc.). This method can be applied to all types of reinforcing fibers, from short fibers to continuous fibers, and is economically advantageous because it has a small number of steps.
Since it is oriented in the (plane direction), the strength properties of the sheet and its stability are also good.

However, from the viewpoint of workability, the fiber used in the laminating method uses a continuous fiber bundle treated with a sizing agent or a discontinuous fiber mat bonded with a binder, resulting in poor fiber dispersibility. There is a drawback that the uniformity of fiber filling during molding is poor.

In order to improve this point, JP-A-3-4774
No. 0 proposes a method in which a bundle of short fibers having a fiber length of 50 mm or less is opened and then accumulated on a conveyor by an air stream, and the obtained fiber mat is laminated with a resin layer. The fiber-opening process in this method is performed in order to change the drop point of the fibers when the cut fibers are accumulated by the air flow (the opened fibers fly farther and then fall).

Further, in JP-A-3-293104, a continuous fiber bundle is passed through a fluidized bed of a thermoplastic resin powder fluidized by an air stream to open the fiber bundle, and at the same time, a thermoplastic resin is added to the fiber. After applying the powder and removing the excess resin,
Disclosed is a method for producing a fiber-reinforced thermoplastic resin sheet, which is cut into short fibers, accumulated on an endless belt, and laminated with a thermoplastic resin sheet. The fiber-opening process in this method is for adhering the thermoplastic resin powder to the inside of the fiber bundle in the fluidized bed.

In all of these methods, since the reinforcing fibers are short fibers having a length of less than 50 mm, the physical and mechanical properties of the fibers are not affected by the opening. Therefore, the opening is not intended to be used to improve these characteristics.

[0009]

It is known that the stampable sheet has properties that change depending on the type of the thermoplastic resin and the reinforcing fiber used, the configuration and form of the fiber, and the like. The characteristics required for stampable sheets differ depending on the application, but for automobile parts, especially automobile exterior parts, in addition to being high strength, energy absorption at the time of destruction is also taken into consideration from the viewpoint of ensuring safety at the time of collision. Materials with high characteristics are desired.

An object of the present invention is to provide a method for producing a stampable sheet suitable for the production of automobile parts, which has good formability, shows stable high strength, and is excellent in energy absorption characteristics at the time of breaking. Is.

[0011]

DISCLOSURE OF THE INVENTION The inventors of the present invention have searched for a method of improving energy absorption characteristics at the time of breakage while ensuring high strength and stability of strength characteristics in a stampable sheet. First, comparing the papermaking method and the lamination method,
The papermaking method is advantageous in terms of energy absorption characteristics at the time of breaking because of good dispersibility of the fibers, but generally, since the fibers are short and three-dimensionally oriented, the strength characteristics are low and unstable. Therefore, it is not suitable for applications that require stable and high strength such as automobile parts. Therefore, the studies were repeated by focusing on the lamination method in which the reinforcing fibers are concentrated and oriented in the plane direction and exhibit stable high strength.

As a result, the stampable sheet having the reinforcing fiber layer made of continuous fibers had a high strength, but the fiber filling property was not good and the energy absorbing property at the time of breaking was poor. On the other hand, a stampable sheet in which the reinforcing fiber layer is composed of short fibers having a length of less than 50 mm has uniform fiber filling property, but the fiber length is too short, so that the strength is insufficient even when formed by the lamination method, Also, the energy absorption characteristics at the time of destruction were not good.

On the other hand, the stampable sheet in which the reinforcing fiber layer is composed of discontinuous long fibers having a length of 50 mm or more has high strength and is excellent in stability of strength. Further, this sheet also had relatively good energy absorption characteristics at the time of breaking, but when the reinforcing fiber was opened before the lamination step, the fiber filling property was further improved, and the adhesion surface area between the resin and the fiber was increased. As a result of the increase, it has been found that the energy required for peeling between the resin and the fiber is increased, the energy absorption characteristics at the time of breakage are further improved, and the above object can be achieved.

Here, in the present invention, in the production of a fiber-reinforced thermoplastic resin sheet comprising laminating a reinforcing fiber layer and a resin layer, the reinforcing fiber layer is composed of discontinuous long fibers having a length of 50 mm or more, The gist is a method for producing a long fiber-reinforced thermoplastic resin sheet, which comprises subjecting a reinforcing fiber to an opening treatment immediately before lamination.

The reinforcing fiber layer may be a reinforcing fiber mat composed of long fibers having a length of 50 mm or more. In this case,
After opening this with one or more rolls,
Laminate with a resin layer. In addition to the long fibers, the reinforcing fiber layer may further include continuous fibers that have been subjected to an opening process and are oriented in one direction.

[0016]

FIG. 1 (a) shows an example of a standard manufacturing process of a stampable sheet by the laminating method. The manufacturing process is
It consists of four steps: a reinforcing fiber supplying step, a laminating step, a laminated sheet heating / pressurizing step, and a manufacturing sheet cutting step.

In the supplying step, the resin layer and the reinforcing fiber layer are supplied to the manufacturing step. The resin layer may take the form of a preformed thermoplastic resin sheet or film, or a dispersion of molten resin or resin powder from thermoplastic resin pellets. In the case of a molten resin or resin powder dispersion, a suitable support (belt etc.) is used. On the other hand, as the reinforcing fiber layer, a preformed fiber sheet (eg, roving, chopped strand mat, etc.) is generally used in terms of work efficiency.

In the laminating step, at least one layer of the supplied resin layer and one layer of the reinforcing fiber layer are laminated while being sent to the next heating / pressurizing step by a conveyor. Generally, both surfaces are resin layers on the outer surface, and reinforcing fiber layers and resin layers are alternately laminated on the inside, but the order of lamination is not particularly limited.

In the heating / pressurizing step, while heating the laminated sheet obtained in (1), the resin is melted and impregnated into the fibers by pressing between the upper and lower belts, and integrated by heat fusion. A laminated sheet of fiber-reinforced thermoplastic resin is obtained. Although the illustrated example is an example of a belt press, pressure may be applied by a roll press.

In the cutting step, the obtained laminated sheet is cooled and then cut into a predetermined length by an appropriate cutter to obtain a stampable sheet product. Molding of the obtained stampable sheet is performed by cutting the cut sheet (blank) obtained by cutting into an appropriate size according to the size of the molded product and heating and softening the heated blank immediately into the press die to a predetermined number. Then, compression molding is performed, and after cooling, the molded product is taken out.

According to the invention, the reinforcing fiber layer has a length of 50 mm.
The above-described discontinuous continuous fibers are used, and before the laminating step, that is, during the feeding step or during the laminating step with the feeding step, the reinforcing fiber opening treatment is performed.

When the reinforcing fibers are short fibers having a length of less than 50 mm, the resulting stampable sheet has a uniform fiber filling property, but since the fiber length is too short, the strength is insufficient and the fibers are broken. It is also inferior in energy absorption characteristics. The upper limit of the fiber length is not particularly limited, but if it is too long, the uniformity of the fiber filling will be deteriorated, so it is usually preferable to set it to 80 mm or less. If there are variations in the fiber length,
The average fiber length may be 50 mm or more.

If the reinforcing fiber layer is pre-opened, the contact surface area between the resin and the fiber is increased, and the energy required for peeling between the resin and the fiber is increased, so that the energy absorption characteristic at the time of breakage is improved. Therefore, the energy absorption property at the time of breaking is improved according to the degree of opening, but in the present invention, it is not necessary to completely open the reinforcing fiber layer into single fibers, and the desired breaking energy is obtained. The fibers may be incompletely opened to such an extent that the absorption characteristics are improved.

However, it is difficult to handle the opened fiber-reinforced layer in the continuous manufacturing process of the laminating method, not only the work efficiency is deteriorated, but also the work environment is deteriorated because the spread fibers are scattered in the air. Therefore, it is preferable to open the reinforcing fibers immediately before the laminating step. The fiber-opening treatment can be carried out by using one or more sets of rolls and passing a reinforcing fiber between the rolls to open a part of the fibers. By supplying the reinforced fibers thus opened, it is possible to obtain a stampable sheet having a uniform fiber filling property and a good energy absorption property at the time of breaking, while ensuring strength stability.

In the case where the reinforcing fiber layer is supplied in the form of a preformed reinforcing fiber mat composed of long fibers having a length of 50 mm or more, between the supplying step and the laminating step,
It is convenient to perform a fiber-opening treatment with a group or two or more groups of fiber-opening rolls, and then laminate the resin layer.

The commercially available preformed mat-shaped reinforcing fiber layer, which is generally bonded between the fibers with a binder for easy handling, has a poor dispersibility of the fibers and is filled with the fibers. However, when the fiber-spreading treatment is performed according to the present invention to eliminate the bond between the fibers, the dispersibility of the fibers is improved and the fiber filling property is improved. It becomes uniform, and the energy absorption characteristics at breakage are also improved.

Further, the reinforcing fibers may further contain continuous fibers in addition to the above-mentioned discontinuous continuous fibers which have been subjected to the fiber opening treatment. By incorporating continuous fibers, the tensile strength and energy absorption characteristics of the obtained stampable sheet can be increased. Also in this case, the continuous fiber is subjected to the fiber-spreading process and is oriented in one direction to be mixed in the reinforcing fiber layer.

Generally, the continuous fibers are supplied in the form of continuous fiber bundles (eg rovings or strands). The supplied continuous fiber bundle is subjected to a fiber-spreading process by one or two or more sets of fiber-spreading rolls during the supply step or between this step and the laminating step, as in the case of long fibers. It is sent to the laminating process together with the long fiber sheet and laminated with the resin layer. Alternatively, the continuous fiber bundle and the long fiber sheet may be put together and then subjected to a fiber-spreading process. As the continuous fibers, a unidirectionally oriented fiber mat in which weft yarns are passed in advance may be used.

Since continuous fiber bundles such as rovings are generally treated with a sizing agent in order to improve workability, the fiber bundles are not loosened even if laminated molding is performed without performing the fiber opening treatment. Therefore, the dispersion of the fibers in the obtained stampable sheet molded product is insufficient, and the energy absorption property at the time of breaking is deteriorated. According to the present invention, if the opening process is performed in advance,
The fibers are loosened during the lamination molding, and a stampable sheet molded article in which the long fibers are sufficiently dispersed is obtained.

In the fiber-opening process, in both the case of the continuous fiber and the continuous fiber, it is better to perform the fiber-opening process by using two or more sets of rolls.
The opening effect is increased. The arrangement direction of the opening roll is not particularly limited, and the rotation direction of the roll may be parallel or perpendicular to the traveling direction of the reinforcing fibers. However, as shown in FIG. 2, when one or more rolls are arranged in the vertical direction, The spread efficiency becomes better.

The shape of the opening roll may be an ordinary cylindrical roll, but in order to increase the degree of opening, it is preferable that the surface has irregularities as illustrated in FIGS. 3 and 4. As for the unevenness, the roll itself may have unevenness, or the unevenness may be formed by a rubber pad or the like.

The roll interval can be adjusted to a desired interval,
Depending on the type of reinforcing fiber passing through the roll, adjustment is made so as to produce a clearance that does not damage the reinforcing fiber itself. Also, the rotation speed of the roll can be set freely for both upper and lower, but it is better to set the rotation speed of the upper and lower rolls differently.
The shear force is further applied to the fiber bundle to improve the degree of opening. However, if you set the rotation speed ratio of the upper and lower rolls to 10 times or more,
There is a high possibility that the shear force will be applied too much and the fiber itself will be destroyed.

In the method of the present invention, the types of the thermoplastic resin and the reinforcing fiber are not particularly limited, and various resins and reinforcing fibers conventionally used in the fiber-reinforced thermoplastic resin composite material can be used. .

Examples of suitable thermoplastic resins include polyolefin resins such as polyethylene and polypropylene, polystyrene resins, polyamide resins, polyester resins,
Examples thereof include polycarbonate resin, polyvinyl chloride resin, polyacetal resin, and copolymer resins or blends thereof. The resin may contain one kind or two or more kinds of various additives such as a stabilizer, a lubricant, a plasticizer, a processing aid, a colorant, a filler, an antioxidant and an ultraviolet absorber.

The reinforcing fibers are generally glass fibers, but other inorganic fibers such as carbon fibers, boron fibers, metal fibers, ceramic fibers, and organic fibers such as aramid fibers can also be used.

The reinforcing fiber content in the stampable sheet is preferably 75% by weight or less. When the amount of the fibers is larger than this, the impregnation property of the resin into the fibers is remarkably deteriorated, and the dispersibility and strength characteristics of the fibers are deteriorated. When continuous fibers are used in combination with continuous fibers as the reinforcing fibers, the amount of continuous fibers is preferably 40% by weight or less based on the entire sheet.

[0037]

EXAMPLES Example 1 Polypropylene pellets (BCO 8
B, made by Mitsubishi Yuka Co., Ltd.), a resin sheet with a thickness of 700 μm made of sheet-shaped glass chopped mat (CM 450, made by Asahi Fiber Glass, fiber length = 55 m) as a reinforcing fiber layer.
m, basis weight = 450 g / m ² ), according to the method of the present invention,
A stampable sheet was produced by the laminating method.

The opened rolls used were stainless steel corrugated rolls (roll diameter 150 mm, corrugation amplitude 30 m, both of the upper and lower rolls having the corrugated concavo-convex shape shown in FIG. 3).
m). Three sets of the corrugated rolls were arranged, and the rolls were rotated in the order of the parallel direction, the right angle direction, and the parallel direction with respect to the sheet traveling direction, as shown in FIG. The clearance between the upper and lower rolls of these opening rolls was 1.2 mm, and the roll rotation speed was adjusted so that the sheet moving speed was 300 mm / sec.

The supplied reinforcing fiber sheet (glass chopped mat) is continuously passed between the above-mentioned three sets of opening rolls to perform an opening process, and three reinforcing fiber sheets thus opened are used to form four resin sheets. Alternately stacked to form a laminated body,
This laminated body was sent to a belt press and pressed at a pressure of 150 kgf / cm ² while being heated to 220 ° C. to be laminated and formed into a sheet.

After cooling, the obtained stampable sheet (thickness 3.0 mm) was subjected to a tensile strength test and a drop impact test,
The strength stability and energy absorption characteristics were evaluated. As shown in Table 1, the stampable sheet obtained in this example had an energy absorption improvement of 12% as compared with the stampable sheet using the unopened fiber sheet of Comparative Example 1.

Example 2 A stampable sheet was produced with the same materials and method as in Example 1 except that the opening roll used was changed. As shown in FIG. 4, the opening roll used in this example is a cylindrical stainless steel roll having a diameter of 100 mm and a lotus leaf-shaped groove having an angle of 45 degrees at a pitch of 5 mm and a thickness of 7 mm. It was a rubber sheet adhered. The clearance between the upper and lower rolls is about 1.5 mm, and 5 sets are arranged so that the roll rotation direction is parallel → right angle → parallel → right angle → parallel direction to the sheet traveling direction, and the roll moving speed is 300 mm / sec. Let it pass. The performance of the obtained stampable sheet was evaluated in the same manner as in Example 1. As a result, as shown in Table 1, the energy absorption was improved by 18% as compared with Comparative Example 1.

Comparative Example 1 Example 1 was repeated except that the reinforcing fiber sheet was laminated with the polypropylene sheet as it was without performing the fiber-opening treatment with the fiber-opening roll. The tensile strength and energy absorption characteristics of the obtained stampable sheet were measured in the same manner as in Example 1 and the results are shown in Table 1.

Comparative Example 2 The same polypropylene sheet as in Example 1 was used as the thermoplastic resin layer, and a sheet-like glass chopped mat (CM 450, made by Asahi Fiber Glass, fiber length = 12.5) made of short fibers as the reinforcing fiber layer. mm, basis weight = 450 g / m ² ) was opened in the same manner as in Example 1 and laminated so that the glass content was the same as in Examples 1 and 2, and I got a stampable sheet in the same way. The tensile strength and energy absorption characteristics of the obtained stampable sheet were measured in the same manner as in Example 1 and the results are shown in Table 1.

[0044]

[Table 1]

Example 3 As the thermoplastic resin layer, the same polypropylene sheet as in Example 1 was used, and as the reinforcing fiber layer, the same sheet-like glass chopped mat made of non-continuous long fibers as in Example 1 and continuous fiber were used. A stampable sheet was prepared by using glass roving in combination with the same method as in Example 1 and passing the both through an opening roll to perform opening treatment.
The content of discontinuous long fibers and continuous fibers in this stampable sheet was 20% by weight. When the obtained stampable sheet was evaluated in the same manner as in Example 1,
As shown in Table 2, the energy absorption was improved by 12% as compared with the unopened product of Comparative Example 3.

Example 4 A stampable sheet was prepared by using the same material and method as in Example 2, but the same continuous glass fibers that were oriented in one direction and opened in the same manner as in Example 3 were used in the reinforcing fiber layer. Mixed in proportion. As shown in Table 2, the obtained stampable sheet has energy absorption higher than that of the unopened product of Comparative Example 3.
Improved by 10%.

Comparative Example 3 A reinforcing fiber sheet made of discontinuous long fibers and a unidirectionally oriented continuous fiber bundle (glass roving) were not subjected to the opening treatment, except that they were laminated with the polypropylene sheet as they were. A stampable sheet was prepared in the same manner as in Example 3. Table 2 shows the results obtained by measuring the tensile strength and energy absorption characteristics of the obtained stampable sheet in the same manner as in Example 1.

[0048]

[Table 2]

[0049]

EFFECTS OF THE INVENTION According to the present invention, by using discontinuous long fibers having a length of 50 mm or more as reinforcing fibers, and by performing the opening treatment of the reinforcing fibers immediately before lamination, the fibers are remarkably superior to the case of using short fibers. It becomes possible to manufacture a stampable sheet having an improved energy absorption characteristic while maintaining a high strength level and strength stability equivalent to those of an unopened product. In addition, when the continuous fiber is mixed into the reinforcing fiber layer in addition to the discontinuous long fiber, the tensile strength and the energy absorption property are further improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a manufacturing process of a stampable sheet by a laminating method.

FIG. 2 is a diagram showing an example of the arrangement of rolls used for the reinforcing fiber opening of the present invention.

FIG. 3 is an explanatory diagram showing a concavo-convex shape of an opening roll.

FIG. 4 is an explanatory diagram showing another uneven shape of the spread roll.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location B29L 9:00 (72) Inventor Hiroshi Kumagai 4-53-3 Kitahama, Chuo-ku, Osaka City Sumitomo Kinen Industry Co., Ltd.

Claims (3)

[Claims] 1. A method for producing a fiber-reinforced thermoplastic resin sheet comprising laminating a reinforcing fiber layer and a resin layer, wherein the reinforcing fiber layer comprises discontinuous long fibers having a length of 50 mm or more, and the reinforcing fibers are laminated before lamination. A method for producing a long fiber-reinforced thermoplastic resin sheet, which comprises subjecting the fiber to an opening treatment. 2. The reinforcing fiber layer is a reinforcing fiber mat composed of long fibers having a length of 50 mm or more, and the mat is opened with one or more rolls and then laminated with a resin layer. The method described in 1. 3. The method according to claim 1, wherein the reinforcing fiber layer further comprises continuous fibers that have been subjected to an opening treatment and are oriented in one direction.