JP2000167942A - Production of thermoforming composite resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a thermoforming resin excellent in dimensional stability and mechanical strength. SOLUTION: A liquid crystal fiber reinforced composite material is produced by a method wherein a mixture of a polyolefin resin and a liquid crystal resin having a liquid crystal transition temp. (Tc) higher than the m.p. of the polyolefin resin is extruded while stretched at temp. equal to or higher (Tc) of the liquid crystal resin and the extruded composite resin is cooled to (Tc) or lower. In this case, a process for extruding the mixture into a strand shape by using a strand die 21, a process for stretching the strand-shaped composite resin extruded from the outlet of the strand die in such a state that the temp. of the resin is equal to or higher than (Tc) so that a stretching speed becomes 0.5-20 times/sec and a stretch ratio becomes 2-50 times to take over the stretched resin, a process for guiding the strand-shaped composite resin to a water tank 4 within [(stretch ratio/stretching speed)-2] sec [(stretch ratio/stretching speed +5] sec from the start of stretching to quench the same to (Tc) and a process for cooling the temp. of the composite resin to below (Tc) are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a composite resin for thermoforming, and more particularly to a method for producing a composite resin for thermoplastic molding having excellent dimensional stability and mechanical strength.

[0002]

2. Description of the Related Art Conventionally, molded articles made of synthetic resin having high strength, high rigidity and dimensional stability include molded articles made of plastic and fiber reinforced resin mixed with reinforcing materials such as glass fiber and carbon fiber. Moldings have been proposed. Also,
In recent years, as a synthetic resin molded product with high strength, high rigidity, and excellent dimensional stability in which glass fibers and carbon fibers are not mixed,
A composite material using a thermoplastic liquid crystal resin as a reinforcing fiber has been developed.

In general, it is well known that liquid crystal resins are in a liquid crystal state in a temperature range higher than a liquid crystal transition temperature, and are easily oriented and fiberized by an external stress such as a shearing force. JP-A-1-320128
Japanese Patent Application Laid-Open Publication No. H11-157, discloses a method in which a thermoplastic resin and a liquid crystal resin are extruded while being stretched at a liquid crystal transition temperature or higher, and then cooled and molded.

[0004]

However, according to the study of the present inventor, as described in the above-mentioned publication, in a method of cooling after extruding a thermoplastic resin and a liquid crystal resin while stretching them at a liquid crystal transition temperature or higher, If the cooling rate after stretching is low, the stretching conditions are such that the liquid crystal resin that has been bent into fibers is unable to maintain the fibrous state due to the heat of the molded body and is relaxed and aggregated, and the physical properties of the molded composite are reduced. Unless the conditions, such as cooling conditions and cooling conditions, which are not described in the above-mentioned publication are grasped in advance, it has been found that a molded product having good physical properties cannot be obtained. An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a method for producing a thermoforming composite resin having excellent dimensional stability and mechanical strength.

[0005]

In order to achieve the above object, the present invention provides a mixture of a polyolefin resin and a liquid crystal resin having a liquid crystal transition temperature higher than the melting point of the resin. A liquid crystal fiber reinforced composite material in which the extruded composite resin is cooled to a liquid crystal transition temperature of the liquid crystal resin or lower, wherein the mixture is extruded into strands using a strand die. And stretching the strand-like composite resin extruded from the strand die outlet in a state where the temperature of the composite resin is in the temperature range equal to or higher than the liquid crystal transition temperature of the liquid crystal resin, and the stretching speed is 0.5 times / sec to 20 times. / Stretching at a rate of 2 to 50 times the stretching ratio and a temperature of the strand-like composite resin after starting the stretching ((stretching ratio Stretching speed) -2) s - ((draw ratio /
A step of rapidly cooling to a liquid crystal transition temperature of the liquid crystal resin in (stretching speed) +5) seconds, and a step of cooling the temperature of the strand-like composite resin to less than the liquid crystal transition temperature of the liquid crystal resin. A method for producing a liquid crystal fiber reinforced composite material.

Hereinafter, the present invention will be described in more detail. In the present invention, the “stretching speed” refers to a stretching ratio per second, and the “stretching ratio” refers to “cross-sectional area immediately after extrusion / cross-sectional area after stretching” of a strand. As the polyolefin resin used in the present invention,
There is no particular limitation as long as it is extrudable, and typical examples include polyethylene and polypropylene. These may use a single resin or a plurality of types of polyolefin resins.

[0007] When a crosslinkable resin is contained in at least a part of the polyolefin resin, the crosslinkable resin is preferably crosslinked to improve heat resistance and mechanical strength.
The method of crosslinking is not particularly limited, for example, an electron beam crosslinking method of irradiating ionizing radiation such as an electron beam, a chemical crosslinking method using an organic oxide, or a silane crosslinking method using a silane-modified resin. And the like.

On the other hand, the liquid crystal resin is not particularly limited as long as it has a liquid crystal transition temperature higher than the melting point or melting temperature of the polyolefin resin, but the liquid crystal resin is formed into a fibril shape in the polyolefin resin. For ease of use, thermoplastic liquid crystal polyester and thermoplastic polyester amide are preferred. Specifically, Vectra (manufactured by Polyplastics), Sumika Super (manufactured by Sumitomo Chemical Co., Ltd.), Zyder (manufactured by Amoco), rod run (unitika) Commercially available products such as those manufactured by the company are preferred examples.

Further, if necessary, a mixture of a liquid crystal resin and a polyolefin resin may be added with a compatibilizer before or during molding in order to improve the mutual compatibility according to the composition of the liquid crystal resin and the polyolefin resin. Good. Examples of the compatibilizer include those obtained by copolymerizing an olefin component and a styrene component or an aromatic polyester component, an olefin resin having a maleic acid component or an acrylic acid component, and an olefin resin copolymer having a glycidyl methacrylate component. The number of parts to be added of the compatibilizer is appropriately selected depending on the composition and ratio of the mixed system.

The mixing ratio of the liquid crystal resin to the polyolefin resin is appropriately selected depending on the composition of the polyolefin resin and the performance required for the product, as long as it is within a concentration range in which the composition as a whole can be extruded. However, if the amount is too small, it is difficult to exhibit the effects of the present invention. If the amount is too large, the liquid crystal resin is difficult to disperse in a fibril shape, so that a sufficient reinforcing effect is also hardly exhibited. Therefore, in the total amount of the polyolefin resin and the liquid crystal resin, the liquid crystal resin is usually 0.5 to
The range is 50% by weight, preferably 1 to 25% by weight, more preferably 3 to 20% by weight.

Incidentally, additives such as a flame retardant, a filler, an antioxidant, a nucleating agent, a pigment and the like may be added to the above mixture as long as the effects of the present invention are not impaired. Such additives are widely known. For example, as the flame retardant, hexabromobiphenol ether, phosphorus-containing flame retardants such as decabromodiphenyl ether, melamine derivatives,
There are inorganic flame retardants and the like.

[0012]

Next, an embodiment of the present invention will be described.
This will be described in detail below. In the method for producing a composite resin for thermoforming of the present invention, first, a mixture of a polyolefin resin and a liquid crystal resin having a liquid crystal transition temperature higher than the melting point of the resin is melt-kneaded at a temperature equal to or higher than the liquid crystal transition temperature of the liquid crystal resin, A strand-like composite resin in which a liquid crystal resin is dispersed in a fibril shape is obtained by extruding from a strand die. At this time, the strand die is passed at a shear rate at which the liquid crystal resin becomes fibrous in the polyolefin resin.

The shear rate is usually 1 × 10^Two-10
^Five/ Sec, preferably 3 × 10^Two-10 ^Four/ Sec. This
Liquid crystal resin in a mixture extruded at a shear rate in the range of
Is likely to fibrillate due to the shearing action of the fluidized part
It is. As the extrusion method, any conventionally known method is adopted.
Frequently, for example, single screw extruders and twin screw extruders are used. S
The shape of the strand die is not particularly limited.
However, for example, one pore 11 as shown in FIG.
Strand die 21 having a circular cross section as shown in FIG.
Disk-like strand in which a large number of fine pores 12 are radially provided.
Doddy 22, a large number of pores 13 as shown in FIG.
A rectangular strand die 23 provided by way of example is illustrated.
From the pores 11, 12, and 13 of the strand die,
It is preferable to extrude a rod-shaped strand die of about 10mm.
New

The strand-like composite resin extruded from the strand die is stretched in a state where the temperature of the composite resin is in a temperature range not lower than the liquid crystal transition temperature of the liquid crystal resin. Stretching is preferably performed by taking up the extruded strand-like composite resin at a high speed by the take-up machine 3. The timing for starting the stretching is not particularly limited as long as the temperature of the strand-like composite resin is in a temperature range equal to or higher than the liquid crystal transition temperature of the liquid crystal resin.However, it is better to start stretching immediately after the strand-like composite resin is extruded from the die. Is preferable because the effect of fibrillation of the liquid crystal resin due to the shearing of the liquid crystal resin is not reduced, and the efficiency of fibrillation is good.

At this time, the film is drawn at a stretching ratio of 2 to 50 times while stretching at a stretching speed of 0.5 to 20 times / second. If the stretching speed is less than 0.5 times / second, the time required for stretching to a desired stretching ratio becomes longer, and the liquid crystal resin which has been bent into fibrils is relaxed and aggregated by the heat of the extruded strand-like composite resin. Also, if rapid cooling is performed at a high cooling rate to prevent its relaxation and aggregation, the liquid crystal resin will solidify without being stretched during stretching, and the fibril diameter will be large, and the aspect ratio will be reduced. The reason for this is that the physical properties of the formed composite are reduced due to the increase in size.

When the stretching speed exceeds 20 times / second, the extruded strand-like composite resin is cut off midway immediately after the resin comes out of the die because instantaneous tensile stress is applied to the resin. Since the extruded strand-like composite resin is stretched to a desired stretching ratio before the temperature of the extruded strand-like composite resin reaches the liquid crystal transition temperature, the extruded strand-like composite resin itself is possessed by the bent fibrillated liquid crystal resin. The fibril diameter becomes thicker due to relaxation and aggregation due to heat, resulting in a large aspect ratio. If the process is continued, a problem occurs that the extruded strand-like composite resin is cut off in the middle.

If the stretching ratio is less than 2 times, the liquid crystal resin dispersed in the polyolefin does not fibrillate sufficiently by stretching, and if it exceeds 50 times, the extruded strand-like composite resin breaks during molding. Or molding may be difficult. The extruded, stretched, or stretched strand composite resin is quenched to the liquid crystal transition temperature of the liquid crystal resin by an arbitrary method. The quenching time at that time is from [(stretching ratio / stretching speed) -2] seconds to [(stretching ratio / stretching speed) +5] seconds from the start of stretching.

If the time for rapidly cooling the temperature of the strand-like composite resin to the liquid crystal transition temperature is [(stretch ratio / stretch rate) +5] seconds or more from the start of stretching, the fibrillated liquid crystal resin is extruded. If the stretched strand-shaped composite resin itself is relaxed and agglomerated by the heat held therein, or if it is less than [(stretch ratio / stretch speed) -2] seconds from the start of stretching, the liquid crystal resin is stretched during stretching. Since the fibers are solidified without being stretched, the diameter of the fibrils is increased, and the aspect ratio is increased, so that the physical properties of the formed composite are reduced.

The timing of the start of the quenching is not particularly limited, but it is preferable to start the quenching immediately after being extruded from the die and simultaneously perform the stretching and the quenching, because of good production efficiency. The strand-like composite resin quenched to the liquid crystal transition temperature is then further cooled to below the liquid crystal transition temperature, that is, the shape and shape of the molded product.
It is necessary to cool to a temperature at which the dimensions do not change plastically, and usually to ambient temperature.

As means for cooling the compact to be cooled, there are a method of passing the compact through a coolant such as a water tank 4, a method of applying cool air to the compact with a blower or the like, and a cooling tank through which the coolant flows. The cooling means is appropriately selected according to the size of the obtained molded product and the molding line. In addition, a conventionally known one for picking up a molded body can be used, and a belt type take-up machine, a caterpillar type take-up machine, a take-up roll and the like are appropriately used.

(Action) According to the method of the present invention, a mixture of a polyolefin resin and a liquid crystal resin having a liquid crystal transition temperature higher than the melting point of the resin is extruded while being stretched at a temperature higher than the liquid crystal transition temperature of the liquid crystal resin. A method for manufacturing a liquid crystal fiber reinforced composite material, wherein the extruded composite resin is cooled to a liquid crystal transition temperature of the liquid crystal resin or lower, wherein the mixture is extruded in a strand shape using a strand die, and extruded from an exit of the strand die. In the state where the temperature of the composite resin is in a temperature range equal to or higher than the liquid crystal transition temperature of the liquid crystal resin, the stretching speed is 0.5 to 20 times / second, and the stretching ratio is The step of drawing while stretching to 2 to 50 times, and the temperature of the strand-like composite resin is set to [(stretch ratio /
A step of rapidly cooling to a liquid crystal transition temperature of the liquid crystal resin in (stretching speed) -2] seconds to [(stretching ratio / stretching speed) +5] seconds, and keeping the temperature of the strand-like composite resin below the liquid crystal transition temperature of the liquid crystal resin. And a step of cooling, so as to obtain a molded article, the obtained molded article,
The liquid crystal resin is well oriented in the extruding direction in a state where the liquid crystal resin is uniformly fibrillated inside, and the strength and rigidity in the extruding direction are improved, and a product having excellent dimensional stability can be obtained.

[0022]

The present invention will be described below with reference to examples.

<Embodiment 1> The entire molding apparatus used in the embodiment was used as a liquid crystal resin shown in FIG.
Trade name: Vectra A950 [liquid crystal transition temperature = 280 ° C,
A mixture containing 14% by weight and 86% by weight of a homoolefin as a polyolefin (melting point: 165 ° C., MI = 0.5 g / 10 min) was used to prepare a mixture containing 14% by weight as measured by DSC (differential scanning calorimeter). 30m set to
m Twin melt extruder 1 to melt and knead
After being extruded in a strand shape by the hole strand die 21 (FIG. 1), drawing was performed while stretching at a stretching speed of 3.5 times / second and a stretching ratio of 10 times, and at the same time, cooling was performed by passing through the water tank 4. .

In the cooling step, the time required until the entire temperature of the composite resin extruded from the strand die is cooled to the liquid crystal transition temperature of 280 ° C. is 3 seconds after the composite resin is extruded from the die and starts stretching. (Stretching ratio / stretching speed = 2.86 seconds), cooling was continued in the water tank 4, and then cooled in an atmosphere to obtain a molded product having good surface properties. The molded article was evaluated according to the following [Evaluation of molded article], and the results are shown in Table 1 together with other examples and comparative examples.

<Example 2> In Example 1, the compounding ratio of the liquid crystal resin and the polyolefin was set to 28% by weight: 72% by weight, and the other conditions were the same as in Example 1 to obtain a molded article having good surface properties. Obtained.

<Comparative Example 1> In Example 1, the stretching speed was 0.4 times / second, and the stretching temperature was quadrupled, and the overall temperature of the composite resin extruded from the strand die was 280 of the liquid crystal transition temperature. The same as in Example 1 except that cooling was performed so that the time until cooling to 10 ° C. was 10 seconds (stretching ratio / stretching speed = 10 seconds) from when the composite resin was extruded from the die and stretching was started. did.

<Comparative Example 2> In Example 1, the time required for the temperature of the extruded composite resin to be cooled to 280 ° C. was 10 seconds from when the composite resin was extruded from the die and started to be taken out (stretch ratio / stretch ratio). The cooling was performed so that the speed was 2.86), and the other conditions were the same as in Example 1.

[Evaluation of molded article] (Tensile strength) A plurality of the obtained strand-like composite materials are arranged in the same direction to form a sheet by hot pressing, and the tensile direction is the direction in which the sheets are arranged when the sheet is formed. A dumbbell test piece was prepared in the same manner as described above, and a tensile test was performed. The preparation of the test piece and the tensile test were conducted according to JIS K
Performed in accordance with 7113.

(Coefficient of thermal expansion) A plurality of the obtained strand-like composite materials are arranged in the same direction to prepare a sheet by hot pressing, and the sheet is placed in a constant temperature bath.
The temperature was raised from 60 ° C. (T1) to 60 ° C. (T2), and the dimensional changes in the length direction of the length L1 at the temperature of 30 ° C. and the length L2 at the temperature of 60 ° C. were measured. The thermal expansion coefficient was determined by dividing by the temperature difference. Thermal expansion coefficient (α) = ((L2−L1) / L1) / (T2
-T1)

(Fiber Diameter Observation) The obtained strand-like composite material was frozen and broken in liquid nitrogen, and its cross section was observed under magnification by SEM (scanning electron microscope). The fibril diameter of 30 liquid crystal resins in the cross-section was observed. Was measured and the average value was determined.

[0031]

[Table 1]

[0032]

The method for producing a composite resin for thermoforming according to the present invention is configured as described above. According to the present invention, the liquid crystal resin is well oriented in the extrusion direction in a state where the liquid crystal resin is uniformly fibrillated inside. In addition, a molded product having improved strength and rigidity in the extrusion direction and excellent dimensional stability can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing one embodiment of a strand die that can be used in a method for producing a composite resin for thermoforming of the present invention.

FIG. 2 is a schematic plan view showing another embodiment of a strand die that can be used in the method for producing a composite resin for thermoforming of the present invention.

FIG. 3 is a schematic plan view showing still another embodiment of a strand die which can be used in the method for producing a composite resin for thermoforming of the present invention.

FIG. 4 is a schematic side view of an entire production apparatus that can be used in the method for producing a composite resin for thermoforming of the present invention.

[Explanation of symbols]

 21, 22, 23 ... Strand die 4 ... Water tank

Continued on front page F term (reference) 4F205 AA03 AA11 AC07 AR06 HA13 HA27 HA34 HA43 HB02 HC02 HC12 HE06 HF01 HG04 HK04 HK07 4F207 AA03 AA11 AC07 AR06 KA01 KB21 KE06 KF01 KJ09 KK54 KM16

Claims (1)

[Claims] 1. A mixture of a polyolefin resin and a liquid crystal resin having a liquid crystal transition temperature higher than the melting point of the resin is extruded while being stretched at a temperature equal to or higher than the liquid crystal transition temperature of the liquid crystal resin. A method for producing a liquid crystal fiber reinforced composite material that is cooled to a temperature equal to or lower than a liquid crystal transition temperature of a resin, comprising: extruding the mixture into a strand using a strand die; and extruding the strand composite resin extruded from a strand die outlet. When the temperature of the composite resin is in a temperature range equal to or higher than the liquid crystal transition temperature of the liquid crystal resin, the stretching speed is 0.5
A step of drawing while stretching at a rate of 2 times / second to 20 times / second so that the stretching ratio becomes 2 times to 50 times, and setting the temperature of the strand-like composite resin to [(stretching ratio / stretching) after starting stretching. A step of rapidly cooling to a liquid crystal transition temperature of the liquid crystal resin in (speed) -2) seconds to [(stretching ratio / stretching speed) +5] seconds; and cooling the temperature of the strand-like composite resin to below the liquid crystal transition temperature of the liquid crystal resin. A method for producing a liquid crystal fiber reinforced composite material.