JP3320929B2 - Manufacturing method of stampable sheet with excellent fluidity during molding - Google Patents

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 stampable sheet having excellent fluidity during molding.

[0002]

2. Description of the Related Art As means for imparting characteristics of high strength and high rigidity while making use of characteristics of thermoplastic resin in molding,
A composite technique by adding a high modulus fiber is known.
The composite thermoplastic resin is used as a material for various structural members that require light weight, high rigidity, and high strength. These materials are usually molded after being heated to the melting point of the thermoplastic resin which is the matrix or higher, and are given a shape, and are particularly suitable for compression molding using a press machine or molding of large parts or The sheet-shaped material is called a stampable sheet. Due to its excellent mechanical strength, workability, and mass productivity, the demand for the stampable sheet is increasing mainly for structural parts for automobiles.

[0003] As a method for producing a stampable sheet, a method (wet method) using a papermaking technique is known. In this method, a discontinuous glass fiber chop and a thermoplastic resin are dispersed in a surfactant-containing aqueous medium containing microbubbles, and this dispersion is prepared on a porous support to prepare a nonwoven web. In this method, the web is heated and pressurized and then solidified to produce a stampable sheet. This technique is disclosed in Japanese Patent Publication No. 2-48423 and Japanese Patent Application Laid-Open No. 60-158227.

[0004]

However, in the stampable sheet obtained by the wet method, if the web forming conditions are inappropriate, the discontinuous glass fibers which are broken into monofilaments are entangled in three-dimensional directions. Structure occurs partially. An example is schematically shown in FIG. The stampable sheet generally receives a compression load W from a direction perpendicular to the sheet surface during compression molding. At this time, the three-dimensional entangled structure B of the glass fibers A in FIG. 4 has a large resistance to the flow of the entire material in the two-dimensional direction. For this reason, the material could not flow to the end of the mold, resulting in insufficient filling. Therefore, establishment of a method of forming a web having no three-dimensional entanglement of glass fibers has been required at an early stage.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for easily producing a stampable sheet which does not have glass fibers entangled three-dimensionally and has excellent fluidity during molding.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have determined that the weight fraction of the discontinuous glass fibers in the dispersion in the papermaking process and the suction speed at the time of papermaking suction of the dispersion are appropriately set. By doing so, it has been found that a web having no three-dimensional entanglement of fibers can be stably manufactured. That is, the present invention provides a discontinuous reinforcing glass fiber of 20 to 70% by weight.
In a method of forming a stampable sheet comprising 30 to 80% by weight of a thermoplastic resin, a dispersion liquid in which glass fibers and a thermoplastic resin are dispersed in a surfactant-containing aqueous medium containing air microbubbles is moved. The glass fiber content of the dispersion is adjusted to 0.01 to 2.5% by weight, and the porous support of the aqueous medium containing a surfactant is used for continuous feeding by feeding onto the papermaking surface of the porous support. 7cm /
This is a method for producing a stampable sheet having excellent fluidity at the time of molding, characterized in that the time is not more than sec.

[0007]

The method for producing a stampable sheet by the wet method of the present invention will be described in detail with reference to FIG. Discontinuous glass fibers and thermoplastic resin are dispersed in a dispersion medium 1 in a surfactant-containing aqueous medium containing air microbubbles. This dispersion is fed through a headbox 2 onto a continuously moving porous support belt 3. A drainage section 4 in a decompressed state is disposed directly below the porous support belt 3, where the aqueous surfactant solution is suction-separated from the dispersion to the drainage section 4 through the porous support belt 3. The non-woven web made of glass fiber and thermoplastic resin formed on the porous support belt 3 is dried by a dryer 5, wound as a coil if necessary, and then heated by a hot press 6. It is heated and pressed to form a dense and solidified stampable sheet.

The structure shown in FIG. 4 which is a problem in the present invention is the same as that shown in FIG.
It is presumed that this is caused by a mechanism schematically shown in FIG. The glass fibers in the dispersion supplied on the porous support belt 3 of FIG. 5 (b) moving continuously through the head box 2 of FIG.
The virgin surface of the porous support belt 3 where no web is deposited is encountered. In this part, the suction resistance is extremely low, and the suction speed D is high. For this reason, the glass fiber is subjected to a sudden suction and pierces the porous support. On the other hand, under standard papermaking conditions, the supply speed of the dispersion is higher than the traveling speed of the belt, so that a portion of the dispersion passes over the already deposited web. At this time, the subsequent glass fiber is captured by the glass fiber pierced into the porous support in the very early stage of papermaking, and develops into a complicated entanglement. In the latter half of the papermaking process, the suction resistance is high and the suction speed is low due to the web being deposited, so that the glass fibers are slowly deposited and no complicated entanglement occurs.

In order to exhibit the effects of the present invention, in order to suppress the piercing of glass fibers into the porous support and the subsequent occurrence of entanglement in the papermaking process, discontinuous dispersion in the dispersion liquid is required as shown below. It is necessary to appropriately set the weight fraction of the glass fiber and the suction speed at the time of papermaking suction of the dispersion. (A) The glass fiber content of the dispersion is 0.01 to 2.5.
It must be in the range of weight percent. Particularly preferably, it is 0.
It is in the range of 1 to 2.0% by weight. If the glass fiber content is more than 2.5% by weight, the probability that fibers defibrated into a monofilament state cross each other increases. As a result, it develops into a three-dimensional entanglement. If it is less than 0.01% by weight, it is not practical in terms of productivity.

(B) When the dispersion is formed on a porous support,
The speed at which the separated aqueous surfactant solution passes through the porous support must be 7 cm / sec or less. Particularly preferably, it is in a range of 6 cm / sec or less. 7cm /
If it exceeds sec, the penetration of the glass fibers in the suctioned dispersion into the belt is increased, causing an entangled structure.

In the present invention, the speed at which the surfactant-containing aqueous medium passes through the porous support is determined by the discharge volume rate of the surfactant aqueous solution discharged from the drain section 4 in FIG. Is defined as the surface divided by the surface of the porous support surrounded by, ie, the papermaking area. The web prepared under the above-mentioned papermaking conditions has less entanglement of the fibers in the dispersion throughout the entire papermaking process.
As shown in (a), the fibers deposit gently on the porous support and on the web. Therefore, the fibers have no three-dimensional entanglement, and have a structure in which all the fibers are arranged in a substantially in-plane direction as shown in FIG. With such a structure, the flow resistance in the two-dimensional direction is significantly reduced, and the flowability of the entire material is improved.

The length of the glass fiber used in the present invention is desirably 6 to 50 mm in order to obtain the reinforcing effect and ensure dispersion in the surfactant-containing aqueous medium. If the fiber length is too small, a sufficient reinforcing effect cannot be obtained. If the fiber length is too large, poor appearance due to agglomeration of the fibers and the occurrence of three-dimensional entanglement of the fibers are caused. The matrix resin may be any thermoplastic resin, and examples thereof include polyolefin, saturated polyester, polycarbonate, polyamide, and thermoplastic polyurethane. Examples of the polyolefin include polyethylene, polypropylene and modified products, copolymers and mixtures thereof, that is, maleic acid-modified polypropylene, acrylic acid-modified polypropylene, ethylene-propylene copolymer and the like.

The shape of the thermoplastic resin is not particularly limited as long as uniform dispersion is ensured in the dispersion and papermaking steps, and powders, pellets, flakes, fibrous materials and the like can be used.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. (Example 1) A stampable sheet was manufactured according to the following procedure based on the process shown in FIG.

In a dispersion tank 1, a 0.08% by weight aqueous solution of sodium dodecylbenzenesulfonate is stirred, and glass fiber (average length 13 mm, diameter 11 μm) and granular polypropylene (diameter 1 mm) are added to the aqueous solution by 0.4% each. % By weight and 0.6% by weight, followed by stirring and dispersion. This dispersion is supplied onto the papermaking surface of the porous support belt 3 moving through the head box 2 to make paper, and the speed at which the separated aqueous surfactant solution passes through the porous support is 6 cm / s.
Under the condition of ec, a web having a basis weight of 2000 g / m ² was prepared. After drying, the web was heated and pressed at 210 ° C. and 5 kg / cm ² , and then cooled and solidified at 20 ° C. and 5 kg / cm ² to obtain a dense sheet.

The obtained sheet was evaluated for fluidity. FIG. 3 schematically shows the procedure. As shown in FIG. 3A, a disk 7 having a radius of 50 mm is cut out from the sheet.
As shown in (b), two disks 7 are stacked and
After preheating to 90 ° C, it is arranged between the press plates 8 at room temperature, and 90 kg / c
Compressed at a pressure of m ² . The ratio r / r ₀ between the average radius (r) after compression and the average radius (r ₀ ) of the sheet before compression was used as an index of fluidity.

In this case, r / r ₀ was 2.13. Example 2 A 0.08% by weight aqueous solution of sodium dodecylbenzenesulfonate was stirred in a dispersion tank 1, and glass fiber (average length: 13 mm, diameter: 11 μm) and granular polypropylene (diameter: 1 mm) were added to the aqueous solution. .05
A sheet was manufactured and evaluated for fluidity in the same manner as in Example 1 except that a dispersion was prepared by adding and stirring and dispersing by weight and 0.075% by weight. In this case, r / r ₀ was 2.10. (Example 3) In the papermaking process, the speed at which the separated aqueous surfactant solution passes through the porous support is 6.5 cm / s.
A sheet was manufactured in the same manner as in Example 1 except that papermaking was performed so as to be ec, and fluidity was evaluated. in this case,
r / r ₀ was 1.89. (Comparative Example 1) A 0.08% by weight aqueous solution of sodium dodecylbenzenesulfonate was stirred in a dispersion tank 1, and glass fiber (average length: 13 mm, diameter: 11 μm) and granular polypropylene (diameter: 1 mm) were added to the aqueous solution. A sheet was produced in the same manner as in Example 1, except that 0.0 wt% and 4.5 wt% were added, and the mixture was stirred and dispersed to prepare a dispersion.
The liquidity was evaluated. In this case, r / r ₀ is 1.15
Met. (Comparative Example 2) In the papermaking process, the speed at which the separated aqueous surfactant solution passes through the porous support was 10 cm / sec.
A sheet was produced in the same manner as in Example 1 except that papermaking was performed so as to obtain c, and fluidity was evaluated. In this case, r
/ R ₀ was 1.08.

From the above, it can be seen that the stampable sheet produced by the method of the present invention has excellent fluidity.

[0019]

Since the stampable sheet produced by the present invention has excellent fluidity, it is a large molded product using a press machine or the like and having a complicated structure, such as a bumper beam with ribs or a concrete panel. , Can be manufactured more easily.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the arrangement of glass fibers in a stampable sheet obtained by the method of the present invention.

FIG. 2 is a schematic diagram illustrating a method for producing a stampable sheet by a wet method according to the present invention.

FIG. 3 is an explanatory diagram showing a method for evaluating the fluidity of a stampable sheet after compression.

FIG. 4 is a schematic cross-sectional view showing an arrangement state of glass fibers of a stampable sheet obtained by a conventional method.

FIG. 5 (a) is a schematic view of a suction deposition state of glass fibers in the first half of the papermaking process in the present invention. (b) It is the model of the suction accumulation state of the glass fiber of the first half of the papermaking process in the conventional method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 dispersion tank 2 head box 3 porous support belt 4 drainage unit 5 dryer 6 hot press 7 disk 8 press plate

Continuation of the front page (72) Inventor Fumiaki Yoshikawa 2-3-2 Uchisaiwaicho, Chiyoda-ku, Tokyo Inside Kawasaki Steel Corporation (72) Inventor Seiji Hanaya 1st Kawasakicho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Corporation Chiba Steel Corporation (56) References JP-A-4-163108 (JP, A) JP-A-2-51536 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29B 15/08

Claims (1)

(57) [Claims] 1. A discontinuous reinforcing glass fiber of 20 to 70% by weight.
In a method of forming a stampable sheet comprising 30 to 80% by weight of a thermoplastic resin, a dispersion liquid in which glass fibers and a thermoplastic resin are dispersed in a surfactant-containing aqueous medium containing air microbubbles is moved. The glass fiber content of the dispersion is adjusted to 0.01 to 2.5% by weight, and the porous support of the aqueous medium containing a surfactant is used for continuous feeding by feeding onto the papermaking surface of the porous support. 7cm /
The method for producing a stampable sheet having excellent fluidity at the time of molding, wherein the time is not more than sec.