JPS63270834A - Composite molding sheet and its production - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a composite molding sheet having a low void ratio and high tensile strength, and a method for producing the same.

(Prior Art) Various composite sheets comprising a thermoplastic organic material and a reinforcing material have been proposed, in which the reinforcing material is impregnated with a thermoplastic organic material having a high melt viscosity.

For example, a method in which a glass fiber strand is opened using static electricity, a thermoplastic organic powder is attached, and then heated and melted to form a tape-bound strand (Japanese Patent Publication No. 47-3848
(Refer to Publication No. 7), a flexible strand is produced by coating a flexible thermoplastic organic on a reinforcing fiber strand to which a thermoplastic organic powder is adhered, and the flexible strand is thermoformed into a fabric or the like. Things (Unexamined Japanese Patent Publication 1986-
(Refer to Publication No. 38156), furthermore, the elastic modulus is 5t/l■1
5 to 50% by weight of the above reinforcing fiber materials and thermoplastic organic cane matrices and lath polymers that can be melted under molding conditions
Mixed fiber mat for forming carbon fiber reinforced composite material consisting of ~50% by weight and both fibers are uniformly mixed (Special Publication Publication No. 62-
19f39) and covered yarns with a core made of a reinforcing material such as carbon fiber and covered with thermoplastic fibers have been proposed, which are then heat-formed under pressure.

(Problems to be Solved by the Invention) In the case where the first glass fiber strand is opened using static electricity, thermoplastic organic powder is attached and then heated and melted, the fiber strand and powder are sufficiently mixed. Not, but also,
Even if a binder is used, the powder often separates before molding, making it difficult to obtain a material with sufficient tensile strength.

The second method, which is thermoformed by using a flexible strand of reinforcing fiber strands to which thermoplastic organic powder is attached, into a fabric, etc., has the same drawbacks as the first method, such as the powder separating and the tensile strength being low. In addition, the method has the drawback that the process is complicated, such as applying the thermoplastic organic powder and the flexible thermoplastic organic powder in separate steps.

A homogeneous mixture of the third carbon fiber and the meltable thermoplastic fibrous matrix polymer is a mat in which both fibers are overlapped in random directions, and therefore when molded, the void ratio is low. Moreover, since it is used in the form of staple fibers, it has the disadvantage of being expensive in terms of process.

Woven fabrics made from covered yarns with a fourth reinforcing material as a core and covered with thermoplastic fibers have the drawbacks of having a large void ratio and low tensile strength after forming. It was also difficult to obtain high-quality products due to the method.

The present invention aims to provide a composite molding sheet that, unlike conventional composite molding sheets, has a low void ratio and high tensile strength, and a method for manufacturing the same.

(Means for solving the problems) The present invention takes the following measures to solve the problems. That is, the present invention provides a knitted fabric for composite molding, characterized in that it is a knitted fabric made of a mixed yarn of 20 to 95% by weight of thermoplastic organic filaments that can be melted under molding conditions and 80 to 5% by weight of heat-resistant filaments. sheet,
and a thermoplastic batter multifilament yarn that can be melted under molding conditions and a heat-resistant multifilament yarn such that the proportion of the latter is 5 to 80% by weight to produce a mixed fiber yarn,
This is a method for producing a composite molding sheet, which is characterized in that the mixed fiber yarn is then used to knit or weave a knitted fabric.

The present invention will now be described in detail. In the present invention, the mixed fiber yarn is used because it is a uniform mixture of heat-resistant filaments and thermoplastic organic filaments that can be melted under molding conditions. This is because when the heat-resistant filaments are melted, the void ratio decreases, and as a result, the tensile strength of the knitted fabric made of the heat-resistant filaments increases. The heat-resistant filament refers to a filament whose melting point or decomposition point is 450° C. or higher, and includes, for example, a filament of wholly aromatic polyamide fiber such as polyparaphenylene terephthalamide fiber, polymetaphenylene isophthalamide fiber, glass fiber, and carbon. Examples include fiber. The proportion of the heat-resistant filaments in the mixed yarn is 5.
~80% by weight. If 5% by weight is ungrooved, the tensile strength of the formed sheet will be low, while if it exceeds 80% by weight, the mixed fiber condition will become poor, the void ratio will increase, and the tensile strength will decrease, so this is preferable. do not have.

On the other hand, the thermoplastic organic filament mixed with the heat-resistant filament must be meltable under molding conditions that do not affect the heat-resistant filament. This is because it can melt the thermoplastic organic filament and serve as an adhesive. In this sense, the thermoplastic organic filaments must be aged between 20 and 95% by weight. If 20% by weight is ungrooved, the adhesive effect will be low, and if it exceeds 95% by weight, the tensile strength of the sheet will decrease. Examples of the thermoplastic organic filament include the following. Polyolefins such as Sunawachi, polyethylene and polypropylene, nylon 6,
Most fibers can be used, including polyamides such as nylon 66, polyesters such as polyethylene terephthalate and polybutylene terephthalate, and highly heat-resistant polymers such as polyphenylene sulfide and polyether ether ketone.

The heat-resistant filament preferably has a thickness of 1 to 10 deniers, more preferably 1 to 3 deniers.

This is to reduce the void ratio and increase the tensile strength.

The thermoplastic organic filament preferably has a thickness of 1 to 10 deniers, more preferably 1 to 3 deniers. This is also to reduce the void ratio and provide an excellent composite molded sheet. The thickness of the mixed fiber yarn is preferably 100 to 10,000 deniers, and the number of filaments is preferably 10 to 1,000. This is based on the reason that it is easy to process in terms of processability and productivity, especially in knitting and weaving processes and melt molding.

Next, when weaving a fabric using the above-mentioned mixed fiber yarn, the textures include not only the three original textures, such as plain weave, twill weave, and satin weave, but also the derived textures, such as basket weave, ridge weave, and broken twill weave. , herringbone weave, etc. In addition, the eye-opening plain weave, which is usually used as the weave structure of reinforced cloth using glass fiber,
Various weave structures can be considered depending on the purpose, such as leno weave and mosao weave, but are not limited to these. Further, when the melt-formed sheet is used as a unidirectional reinforcement or a diagonal laminate, the mixed yarn is used for either the warp or the weft, preferably the warp, and the mixed yarn is used for the other one. This is achieved by weaving the same type of thermoplastic organic fibers as those used in the fabric, laminating them in a predetermined number at a predetermined angle, and then melt-molding them.

Further, when constructing a knitted fabric using the mixed fiber yarn, any of warp knitting, circular knitting, and flat knitting may be used, and any knitting structure may be used. In particular, in order to increase the strength utilization rate of the molded sheet melt-molded after knitting, it is preferable that the mixed fiber yarn is knitted in the form of a lay-in or tuck-in without forming a stitch. Preferably it is a lay-in.

The knitting structure that provides lay-in in the warp knitting method is possible by inserting the warp of the mixed fiber yarn in an O-0/1-1 reed motion, and this knitted fabric is highly reinforced in the machine direction. It becomes something. Furthermore, in order to highly strengthen both the longitudinal and lateral directions, a weft insertion stitch may be added in addition to the warp insertion stitch. These knitted fabrics can be easily knitted using a warp knitting machine.

Circular knitting and flat knitting are excellent in strengthening in only one direction, so by laminating the knitted fabric in a desired direction, it can be used as a unidirectional reinforcing material or a diagonal laminate. In addition, the basis weight of the knitted fabric is preferably 100 to 1000 g/j, particularly preferably 200 to 800 g/j.

Here, a method for manufacturing a composite molding sheet will be explained.

First, a thermoplastic multifilament yarn that can be melted under molding conditions and a heat-resistant multifilament yarn are opened and mixed by applying a high voltage, for example, 100 volts to 5000 volts, or interlace method (
According to Japanese Patent Publication No. 3B-12230 and Japanese Patent Publication No. 37-1175), both multifilament yarns are mixed to produce a mixed yarn.

The inclace method creates two or more vortex turbulent zones approximately parallel to the yarn axis, guides the filament yarn through these zones, and applies tension to the extent that no loops or crimps occur, resulting in a non-bulky, tight, This is a technology for manufacturing strands. The principle of the interlacing method is that the fluid impinges perpendicularly to the filament axis, and at the same time generates a turbulent vortex flow parallel to the filament. The filament bundle is separated into filaments, and at the same time, the individual filaments are pre-combusted and convoluted at random to form an inklace. The degree of interlacing achieved depends on tension, fluid pressure, overfeed rate, filament denier,
It is affected by the number of filaments, the modulus of the yarn, etc.

As a means for blending fibers, the interlacing method is preferable because it allows multifilament yarns to be produced at high productivity and to lower the void ratio when uniformly mixed to form a composite molding sheet. Particularly important points in interlacing are overfeed rate, tension, fluid pressure, denier, and number of filaments. Since heat-resistant fibers generally have a higher relative modulus than thermoplastic organic fibers, it is important to set the overfeed rate to be slightly higher, preferably 5 to 10%. The overfeed rate of the heat-resistant fibers may be set to a base value depending on the content of the thermoplastic organic fibers. Similarly, in terms of tension and fluid pressure, it is important to process heat-resistant fibers under conditions that are slightly higher than those for manufacturing conventional clothing yarns. In particular, the fluid pressure is preferably 10 to 50 psig, preferably 30 to 60 psig, in order to obtain uniform mixing. In addition to the above-mentioned conditions, the denier and number of filaments of the fibers to be mixed are also important for uniform fiber blending. The fiber mixing within the turbulent vortex region is closely related to the linear density, and in order to obtain uniform fiber mixing, it is preferable that the fibers have the same linear density.

Next, using the mixed fiber yarn of the cooking process, it is knitted into plain weave, twill weave, satin weave, and variations thereof of the Mihara weave as described above, or into warp knitting, circular knitting, flat knitting, and other knitted fabrics. In addition, in the case of a woven fabric, the warp yarn density (threads/inch) is preferably 10 to 100 threads/inch, and the weft yarn density (threads/inch) is preferably 10 to 100 threads/inch in order to reduce the void ratio.

By the way, an example of molding using a composite molding sheet made of the knitted fabric obtained as described above will be shown below. The composite molding sheet is cut into a predetermined size for use in a secondary processing process, and a number of sheets equal to the weight of the molded product are piled up to form a blank. Then thermoplastic “
Charge the blank which has been preheated to a temperature above the softening point of the machine fibers, preferably to a temperature sufficient to melt the thermoplastic organic fibers. Finally, the mold is pressed to form the desired shape. The press pressure is usually 5% relative to the projected area.
0 to 150 kg/wa 3 is required, and the faster the pressurizing speed, the more preferably 1 to 2 seconds. The temperature of the mold is preferably below the melting point of the thermoplastic fiber, and the cooling time is determined by the thickness of the thickest part of the molded product.

In addition, the sheet for composite molding uses a blank that has been melt-impregnated with thermoplastic organic fibers in advance using a hot press roll, etc., and is subjected to solid phase stamping by plastic deformation at a preheating temperature below the melting point of the thermoplastic organic fibers. You can also do that.

(Example) Examples 1 to 3 A gusset yarn of polyvara phenylene terephthalamide fiber was used as a heat-resistant multifilament yarn, and a polyethylene terephthalate multifilament yarn (450 denier, 14
4 filaments, phenol/tetrachloroethane = 6
Intrinsic viscosity 0.6 measured at 30°C in a 0/40 mixed solvent
A mixed fiber yarn was produced using an interlaced nozzle in which two pairs of facing fluid conduits (at four locations) were opened at the ratio shown in Table 1. Assuming fluid pressure is 50 psig, approximately 5
The fibers were mixed in a turbulent vortex region at a speed of 0.00 m/min to produce mixed fiber yarns having the proportions shown in Table 1.

Next, the mixed fiber yarn was used as the warp yarn, and the same polyethylene terephthalate multifilament yarn (details are shown in the examples) used for the mixed fiber yarn was used as the weft yarn at the warp density and weft density shown in Table 1. Weaved plain fabric. A sheet cut out from the plain fabric with dimensions of 20 c++ x 20 c+m was used as a blank, and was heated at 80°C for 16 hours, Q, lmmH.
Vacuum drying was performed under the following conditions, and a laminated sheet was made by stacking three sheets so that the mixed fibers of each layer were oriented in the same direction. The laminated sheet is filled into a mold preheated to 300°C, preheated and melted under a light load for 3 to 5 minutes, and then heated to 50 to 70°C.
Heat compression molding was performed at a pressure of 0 KGF/eJ. It was rapidly cooled to 60° C. under pressure before being removed from the mold. By melt-molding in the above procedure, the polyethylene terephthalate filaments used for the mixed fiber yarn and the weft were melted and impregnated, leaving only the polybalara phenylene terephthalamide fiber as a reinforcing material, and a unidirectionally reinforced laminate was obtained. Regarding this unidirectional reinforced laminate, the fiber content (JIS
K 7052) and tensile strength (JISK 70
The axial direction of the polyparaphenylene/nterephthalamide fiber was defined as the longitudinal direction of the experimental specimen in accordance with 54. ) were measured and shown in Table 1. In addition, as a conventional method, a multifilament yarn (380 denier, 260 filaments) of polyvara phenylene terephthalamide fiber is used as the core yarn, and a polyethylene terephthalate multifilament yarn is used as the sheath yarn, and the proportion of the former is 42% by weight. Producing a covered yarn, using the covered yarn as the warp and the same multifilament yarn as in the example as the weft,
Reinforced laminates were produced in the same manner as in the examples, and the fiber content, void ratio, and tensile strength were measured in the same manner and are shown in Table 1. In Table 1, Examples 1 to 3 are related to the present invention, and Comparative Examples 1 to 2 are outside the scope of the present invention.

Table 1 In Table 1, the conventional method uses covered yarn for the warp, but when it is formed into a reinforced laminate, voids occur due to the yarn structure when the thermoplastic filament melts. Therefore, the void ratio was relatively high, and the tensile strength was low despite the high content of heat-resistant filaments. In Comparative Example 1, the tensile strength was low because the ff content of the heat-resistant filament was low. Example 1
Samples No. 3 to 3 had a low void ratio and a high tensile strength because the heat-resistant filament content was at an appropriate level. Although the material of Comparative Example 2 had an extremely high content of heat-resistant filaments and naturally had high tensile strength, it had a high void ratio and was far from being of high quality.

(Effects of the Invention) The composite molding sheet of the present invention is a knitted fabric using a mixed yarn made of thermoplastic filaments and heat-resistant filaments in a specific ratio, so the molded product is The method of the present invention has a lower void ratio and higher tensile strength than the conventional method. A remarkable effect is achieved in that production is possible.

Claims (1)

[Claims] 1. 20-95% by weight of thermoplastic organic filaments that can be melted under molding conditions and 80-5% by weight of heat-resistant filaments.
A sheet for composite molding, characterized in that it is a knitted fabric made of yarn mixed with. 2. Mix a thermoplastic organic multifilament yarn that can be melted under molding conditions and a heat-resistant multifilament yarn such that the ratio of the latter is 5 to 80% by weight to make a mixed fiber yarn;
A method for producing a sheet for composite forming, which comprises then weaving and weaving a knitted fabric using the mixed yarn.