KR101348948B1 - Thermoplastic composite for easy impregnation and manufacture method thereof - Google Patents

Abstract

The present invention is to allow the thermoplastic resin to be easily and uniformly impregnated in the reinforcing material in the implementation of the composite material containing the thermoplastic resin, by thermocompression bonding a plurality of needle mat containing the reinforcing fiber of the resin to a single thermoplastic composite sheet In the construction, each of the needle mats is composed of a needle needle hybrid laminated by alternately stacking a reinforcing fiber layer and a thermoplastic resin film to facilitate the impregnation of the thermoplastic resin in the reinforcing fibers.

Description

Thermo-impregnated thermoplastic composite and its manufacturing method {THERMOPLASTIC COMPOSITE FOR EASY IMPREGNATION AND MANUFACTURE METHOD THEREOF}

The present invention relates to a composite material, and more particularly, to a thermoplastic composite manufacturing method and a thermoplastic composite manufacturing method for allowing a thermoplastic resin to be uniformly impregnated in a reinforcing material in implementing a composite material including a thermoplastic resin.

Conventionally, thermosetting resins such as epoxy resins are mainly used as one material constituting a composite material, but recently, thermoplastic resins are attracting attention as alternatives and are being utilized in various fields.

Thermoplastic composite materials have attracted attention because of their high toughness, which is difficult to realize in thermosetting resins, their impact resistance is good, their molding is easy, their processing speed can be increased, and their repair and repair are easy. Because of this. Moreover, as the industry develops day by day, it is also advantageous that it can solve the problem of waste disposal and recycling such as environmental problems and depletion of limited resources.

Among the thermoplastic composites, long fiber reinforced thermoplastic composites (LFTs) are largely divided into pellets and needle mats.

First, the pellets in the form of LFT pellets are produced in the length of the reinforcing fibers 10 ~ 20mm level, the content of the reinforcing fibers is generally in the range of 30 ~ 60wt.%. LFT pellet is a composite material that is molded by injection molding, and when the LFT pellet is melted in the injection molding machine, the reinforcing fiber is destroyed by friction with the screw, so the actual length of the reinforcing fiber in the molded product is shortened to 2 ~ 5 mm. There is this. In this range, the reinforcing fiber length can be 90% or more in the stiffness characteristic and 80% or more in the stiffness characteristic, but the impact characteristic is very low, which is 40% or less.

As an example of the patent prior art related to the LFT pellet manufacturing method is disclosed in Patent Publication No. 10-2008-0083550 "Long-fiber-reinforced thermoplastic resin pellets and a manufacturing method thereof", Patent Publication No. 10-2010-0071053 "Long-fiber-reinforced thermoplastic resin Impregnating dies for producing molding materials ", Published Patent Application No. 10-2010-0071054" Method for manufacturing long fiber reinforced thermoplastic resin molding material ", etc. are typical.

Needle mats in thermoplastic composites typically have a reinforcing fiber in the range 25 to 100 mm in length and are thermocompression molded in a press form. Therefore, the thermoplastic composite material in the form of needle mat is mostly maintained without breaking the length of the reinforcing fiber. In this range of reinforcing fiber lengths, both stiffness and strength characteristics are 90% or more and impact characteristics are 80% or more.

Thermoplastic composites in the form of needle mats are very advantageous in the case of bumper back beams or underbody covers, which are automotive parts requiring impact properties. In addition, in the case of press molding, since the flow distance is minimized compared to injection molding, excessive fiber orientation due to flow and residual stress caused by this are small, so there are fewer problems of crack generation and crack propagation due to impact. An example of a related patent precedent document using a needle mat-type material is Published Patent Publication No. 10-2010-0046677 "Vehicle Back Beam Manufacturing Method".

On the other hand, in the case of a component having a complicated structure, the pellet-shaped LFT pellet is much more advantageous than the needle mat type. Therefore, there is a situation in which a long fiber reinforced thermoplastic composite material using a needle mat material or a long fiber reinforced composite material is used.

Easily impregnating the thermoplastic resin in the reinforcing fiber layer in the production of the thermoplastic composite material is very important for the manifestation of various advantages of the thermoplastic composite material. In general, thermoplastic resins have poor adhesion to fiber reinforcements due to their inherent properties and are difficult to impregnate.

One of the methods for improving the resin impregnation ease is to approach in the direction of lowering the viscosity of the thermoplastic resin. An example of a representative prior art that lowers the viscosity is Published Patent Application No. 10-2006-0116199, "Improved Glass Mat Thermoplastic Composite Material."

This technique has a low viscosity on the needle mat made of reinforcing fibers, and is a method of preparing a thermoplastic composite material by injecting a monomer or oligomer form and a polymerizable component first, followed by polymerization. In the case of the polypropylene thermoplastic resin, when the molten resin is melted in an extruder, a method of injecting a peroxide component may be used to arbitrarily cut the polymer chain to form a low molecular weight form having a low viscosity.

However, these methods have insufficient disadvantages in considering unstable polymerization products, residual problems of polymerizable components or peroxides, various stabilizers added in the polymerization process, and consequently, uneven molecular weight distribution. Generally, when polymerizing a thermoplastic resin, various stabilizers are added in consideration of the polymerization process and future molding process, and unnecessary residues are removed through a degassing process, which is a subsequent process for the polymer polymerized with an appropriate molecular weight distribution in the reactor. Remove in advance.

Another approach to ensure the ease of impregnation is a method of physically mixing the resin in the form of fibers, as well as reinforcing fibers in the needle mat forming step. An example of the representative prior art is Korean Patent Publication No. 10-2006-0125222, "Method for producing a low specific gravity thermoplastic composite material".

This physical mixing method is a structure that can be easily impregnated by applying heat and pressure because physically mixed reinforcing fibers and resin fibers. However, this physical mixing method has a disadvantage that can not guarantee a uniform mixing.

Accordingly, an object of the present invention is to provide a method for manufacturing a thermoplastic composite and a thermoplastic composite thereof so that the thermoplastic resin can be easily and uniformly impregnated in the reinforcing material in implementing the composite material containing the thermoplastic resin.

According to the above object, the present invention, in the method of manufacturing a thermoplastic composite material, the thermoplastic resin film is inserted between the reinforcing fiber layer to facilitate the resin impregnation to form a multi-layer and the needle to perform the integrated hybrid needle mat as an intermediate material And, it is characterized by consisting of a process of obtaining a thermoplastic composite sheet made of resin impregnation by cooling after at least one of the hybrid needle mat thermocompression.

The reinforcing fibers constituting the reinforcing fiber layer is characterized in that one of glass fiber, carbon fiber, aramid fiber, natural fiber.

In addition, the thickness of the reinforcing fiber layer of the hybrid needle mat is obtained using the impregnation thickness of Darcy's law,

The surface density of the reinforcing fiber layer constituting the hybrid needle mat is determined in consideration of the surface density of the fiber layer according to the molten resin permeability coefficient of Darcy's law and is characterized by being formed at 400 g / m ² or less.

In addition, the present invention, in the construction of a single thermoplastic composite sheet by thermocompression bonding a plurality of needle mats containing reinforcing fibers, each of the needle mats alternate between the reinforcing fiber layer and the thermoplastic resin film to facilitate the impregnation of the thermoplastic resin in the reinforcing fibers. It is an easy-impregnated thermoplastic composite which is composed of a composite needle mat laminated and needling.

The thickness and surface density of each of the reinforcing fiber layers constituting the hybrid needle mat are calculated using Darcy's law and Kozny-Kalman equation.

The thermoplastic resin film is characterized in that the solid film produced using a high viscosity thermoplastic resin of 10 or less melt index.

According to the present invention, thermoplastic resin is used during thermocompression molding by forming a needling hybrid mat by alternately stacking a reinforcing fiber layer and a thermoplastic resin film in the form of a needle mat, an intermediate material for stiffening a long fiber reinforced thermoplastic composite material. There is an advantage that the impregnation into the reinforcing fiber material is made easily and uniformly, and there is also an advantage that it is easy to handle compared to the needle mat made of the existing reinforcing fiber only.

1 and 2 is a block diagram of a manufacturing apparatus of a thermoplastic composite according to an embodiment of the present invention,
3 is a cross-sectional configuration diagram of a needle mat as an intermediate material obtained by the needle mat manufacturing process of FIG. 1;
Figure 4 is a cross-sectional configuration diagram of the preliminary molding material before the injection into the double belt press in FIG.
Figure 5 is a block diagram of a thermoplastic composite sheet produced by thermocompression molding according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the present invention, to realize a thermoplastic material in the form of a needle mat (many mat) having a number of advantages in the commercialization of the thermoplastic composite material, to ensure the ease of impregnation of the thermoplastic resin during thermocompression molding when implemented as a needle mat type thermoplastic composite By using a peroxide, which is a conventional method of glass mat thermoplastic (GMT), it is implemented in a new method different from the conventional method of lowering the viscosity of the molten resin.

That is, in the present invention, when configuring one needle mat as an intermediate material, the reinforcing fiber layer and the thermoplastic resin film are alternately laminated and needled to constitute a hybrid needle mat.

At least one of the hybrid needle mats may be easily and evenly made by impregnating the thermoplastic resin into the reinforcing fiber layer by melting the thermoplastic resin films alternately formed in each needle mat during thermocompression molding.

The present invention is completed in the thermoplastic composite sheet through a two-step manufacturing process shown in Figures 1 and 2 in manufacturing a thermoplastic composite in the form of a needle mat.

1 is a schematic configuration diagram of a needle mat manufacturing apparatus 100 for manufacturing a hybrid needle mat (A) which is an intermediate material according to the present invention, Figure 2 is a hybrid needle mat (A) of the present invention obtained in FIG. It is a schematic block diagram of the thermoplastic composite sheet manufacturing apparatus 200 which impregnates by crimping | molding and makes a thermoplastic composite sheet (C).

In the manufacturing process of Figure 1 is inserted into the thermoplastic resin film (4a) between the reinforcing fiber layer (6a) to form a multi-layer and needling (needling) to obtain an integrated hybrid needle mat (A) as an intermediate material, after this In order to improve the ease of impregnation of the thermoplastic resin during the thermocompression of the manufacturing process of 2, the hybrid needle mat A is configured to have an appropriate level of thickness and surface density of the reinforcing fiber layer 2a.

Referring to Figure 1, the material of the reinforcing fiber layer (2a) constituting the hybrid needle mat (A) of the present invention include glass fiber, carbon fiber, aramid fiber, natural fiber and the like, of which glass fiber is most preferred.

In order to alternately form the reinforcing fiber layer 6a and the thermoplastic resin film 4a in multiple layers on the needle mat A according to the present invention, as many preferable mills as many as the number of forming the reinforcing fiber layer 6a and And the number of thermoplastic resin film feed rolls 4 inserted between the reinforcing fiber layers 6a.

The thermoplastic resin film 4a used in the present invention is a flexible solid film manufactured using a high viscosity thermoplastic resin having a melt index of 10 or less, and will be melted during thermocompression molding in the manufacturing process of FIG. 2.

 The thermoplastic resin film 4a is provided from the plurality of thermoplastic resin film feed rolls 4 and is superimposed on the conveying belt 8, and the grinder 6 is positioned between the thermoplastic resin film feed rolls 4. A reinforcing fiber bundle 2 in the form of a roving is cut to the predetermined length in the grinder 6 and distributed to the conveying belt 8 while being evenly distributed.

Therefore, the thermoplastic resin film 4a and the reinforcing fiber layer 6a are alternately laminated on the conveyance belt 8 to form a multilayer, and the belt is conveyed in the state to be supplied to the needling device portion 8, and the needling device portion ( The needling (niddling) by 8) is formed to form one hybrid needle mat (A) as shown in FIG.

That is, the hybrid needle mat (A) of the present invention is formed by inserting the thermoplastic resin film (4a) between the reinforcing fiber layer (6a) to form a multi-layer and needling to integrate the reinforcing fiber layer (6a) and the thermoplastic resin film (4a) In order to improve the ease of impregnation, the thickness of the reinforcing fiber layer 6a suitable for impregnation is defined based on the impregnation thickness h using the Darcy Law described in [Equation 1].

Equation 1 below is "Darch Law".

= 열가소성수지의 점도[Pa.s], h = 보강섬유층이 요구하는 함침두께.Where v = volumetric flux or superficial velocity [m / s], K = melt permeation coefficient of the fiber tissue [m ² ], ΔP = pressure received through the fiber [Pa],

= Viscosity of thermoplastic resin [Pa.s], h = impregnation thickness required by the reinforcing fiber layer.

The melt resin transmission coefficient K of the reinforcing fiber layer 6a in Equation 1 may be obtained using the Kozeny-Carman equation shown in Equation 2 below.

Where d = diameter of the fiber yarn, e = porosity or porosity of the fiber mat.

)와 보강섬유층(6a)이 요구하는 함침 두께(h)와 함께 반비례 관계에 있음을 알 수 있고, 아울러 도 2의 제조공정에서의 열압착 성형시 프레스(16)에 의해 가해지는 압력(ΔP)에는 정비례 관계임을 알 수 있다. As with Darcy's law of Equation 1, the apparent velocity v of the molten resin showing the ease of impregnation is the viscosity of the thermoplastic resin (

) And the reinforcing fiber layer 6a are in inverse relationship with the required impregnation thickness h, and the pressure ΔP applied by the press 16 during thermocompression molding in the manufacturing process of FIG. 2. It can be seen that the relationship is directly proportional.

)와 프레스에 의해 가해지는 압력(ΔP)은 일정한 값으로 하고, 니들매트(A)를 구성하는 열가소성 수지필름(4a)을 보강섬유층(6a) 사이에 삽입하여 보강섬유층(6a)에 함침가능한 보강섬유층(6a)의 두께(h)를 조절함으로써 함침의 용이성을 향상시킬 수 있다. In the present invention, the viscosity of the thermoplastic resin (

) And the pressure ΔP applied by the press is a constant value, and the reinforcing fiber impregnated into the reinforcing fiber layer 6a by inserting the thermoplastic resin film 4a constituting the needle mat A between the reinforcing fiber layers 6a. The ease of impregnation can be improved by adjusting the thickness h of the fiber layer 6a.

In addition, as the content (weight ratio) of the reinforcing fiber layer 6a increases, the K value shown in the Kozeny-Carman Equation decreases. As the K value decreases, the apparent velocity (v), which indicates the ease of impregnation, decreases, so that the surface density of the reinforcing fiber layer 6a constituting the hybrid needle mat A is increased by the corresponding amount for complete impregnation of the reinforcing fiber layer 6a. It should be small.

In FIG. 1, in the hybrid needle mat A, a thermoplastic resin film 4a and a reinforcing fiber layer 6a are formed using a plurality of thermoplastic resin feed rolls 4 and a mill 6 as shown in FIG. 1. However, one thermoplastic resin film 4a may be stacked in a zigzag manner, and the reinforcing fiber layer 6a may be inserted therebetween.

It will also be apparent to those skilled in the art that the lamination method of the thermoplastic resin film 4a is not always alternate with the reinforcing fiber layer 6a but may be laminated randomly.

Many of the hybrid needle mat (A) made of the intermediate material as described above is used in the manufacturing process of the thermoplastic composite sheet (C) using the double belt press (Double Belt Press) 16 shown in Figure 2, A) is supplied to the double belt press 16 in the state of the preform (B) as shown in FIG.

The thermoplastic resin film 4a alternately inserted into each of the hybrid needle mats A is melted at the hot pressing portion 18, which is the front end portion of the double belt press 16 to which high temperature (for example, 200 to 300 ° C) and high pressure is applied. Evenly impregnated to penetrate each of the reinforcing fiber layer 6a of the hybrid needle mat (A), the cooling crimping unit 20, which is the rear end is solidified by cooling to finally form a composite sheet of the plate shape as shown in FIG. (C) is obtained. That is, the composite sheet C in which the plurality of crimped reinforcing fiber layers 4b in which the resin of the thermoplastic resin film 4a formed in multiple layers is melted and evenly impregnated is integrated is obtained.

In order to confirm the ease of impregnation, the inventors prepared the following experimental examples based on the preparation of 40 wt.% Long fiber reinforced composites made of PP (polypropylene) / GF (glass fiber). At this time, the volume ratio of the glass fiber (GF) as the reinforcing fiber is 18.6%, when the diameter of the reinforcing fiber is 17㎛, the distance between the fibers is 18㎛. Polypropylene (PP) used as the thermoplastic resin film 4 is a film of a specific thickness manufactured using a high viscosity resin having a melt index of 10 or less. The inventors compared the surface density change before and after impregnation to evaluate the ease of impregnation.

(Experimental example 1): Surface density 100 g / m ² Reinforcing fiber needle mat

As Experimental Example 1 for confirming the ease of impregnation, a hybrid needle mat was formed by alternately stacking eight layers of a reinforcing fiber needle mat having a surface density of 100 g / m ² and nine layers of a polypropylene film of thermoplastic resin. In Experimental Example 1, in order for the thermoplastic resin to be completely impregnated in the reinforcing fiber layer constituting the mat, theoretically, three layers of reinforcing fiber should be passed through the Darcy's law. It was analyzed to pass through the reinforcing fiber layer.

Experimental Example 2 Surface Density 400 g / m ² Reinforcing fiber needle mat

As Experimental Example 2 for confirming the ease of impregnation, two layers of a reinforcing fiber needle mat having a surface density of 400 g / m ² and three layers of a polypropylene film of thermoplastic resin were alternately laminated, and in Experimental Example 2, the thermoplastic resin mat In order to be fully impregnated, the theoretically must pass through twelve layers of reinforcing fibers each. When the experimenter measured the surface density change before and after the impregnation, the molten resin did not pass through the reinforcing fiber layer and flowed in the planar direction, and the rate of squeeze out was analyzed as 6.9%.

(Example 3): surface density 800 g / m ² Reinforcing fiber needle mat

As Experimental Example 3 for confirming the ease of impregnation, one layer of a thermoplastic resin polypropylene film was inserted into two layers of a reinforcing fiber needle mat having a surface density of 400 g / m ² . This shows the same effect as using the surface density 800 g / m ² when compared to the correlation with Experimental Example 2, each must pass through 24 layers of reinforcing fibers for complete impregnation. As a result of measuring the surface density change before and after the impregnation, the rate of squeeze out of the molten resin through the reinforcing fiber layer and squeezed out was analyzed as 9.7% for impregnation.

Through the above experimental examples, in the case of PP / GF 40wt.% Long fiber reinforced thermoplastic composite material using a reinforcing fiber having a diameter of 17 μm, the reinforcing fiber needle mat is a thermoplastic resin having a surface density of at least 400 g / m ² or less. A relatively complete impregnation is possible by passing through about 10 levels of reinforcing fiber layers through a hybrid mat integrated by laminating alternately with a film and performing needling.

More preferably, it is advantageous to design to pass about three levels of reinforcing fiber layer 6a by using a surface density of 100 g / m ² of the reinforcing fiber layer 6a as in Example 1 above.

When the needle mat is composed only of ordinary reinforcing fibers, it is common to have a surface density of 1,000 g / m ² of the needle mat, and the preferable surface density of the reinforcing fiber layer 6a of the present invention is relatively smaller than that of the conventional reinforcing fibers. .

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. Therefore, the scope of the present invention should not be limited by the described embodiments, but should be determined by the scope of claims and equivalents thereof.

(2)-Reinforcing fiber bundle (4)-Thermoplastic film feed roll
(4a)-thermoplastic film (6)-grinder
(6a)-reinforcing fiber layer (8)-conveying belt
(10)-Needling Device Part (12)-Mixed Needle Matrol
(16)-Double Belt Press (18)-Heating Crimp
(20)-cooling crimp

Claims (7)

In the thermoplastic composite manufacturing method,
Between multiple thermoplastic resin films adopting a high viscosity thermoplastic resin with a melting index of 10 or less, a reinforcing fiber layer obtained by pulverizing one of glass fibers, carbon fibers, aramid fibers, and natural fibers is formed in multiple layers, and needling is performed. The process of obtaining an integrated composite needle mat as an intermediate material,
Stacking two or more of the hybrid needle mats to obtain a preform,
The preform is supplied to a double belt press to be heated and pressurized and then cooled to obtain a thermoplastic composite sheet impregnated and solidified with a thermoplastic resin film in the reinforcing fiber layer.
The inner center of the preform is easy to impregnate thermoplastic composite manufacturing method, characterized in that a pair of thermoplastic resin film contacted before supplying the double belt press.
According to claim 1, wherein the thickness of the reinforcing fiber layer is obtained by using the impregnation thickness (h) of the equation (1),

(1)
v = volumetric flux or superficial velocity [m / s], K = melt permeation coefficient of the fiber tissue [m ² ], ΔP = pressure received through the fiber [Pa],

= Easy to impregnate thermoplastic composite, characterized in that the viscosity of the thermoplastic resin [Pa.s].
The molten resin permeability coefficient (K) is obtained by using Equation 2,

(2)
d = diameter of the fiber yarn, e = porosity or porosity of the fiber mat, easy impregnated thermoplastic composite manufacturing method.
The method of claim 3, wherein the surface density of the reinforcing fiber layer constituting the hybrid needle mat is formed to be 400 g / m ² or less.
Between multiple thermoplastic resin films adopting a high viscosity thermoplastic resin with a melting index of 10 or less, a reinforcing fiber layer obtained by pulverizing one of glass fibers, carbon fibers, aramid fibers, and natural fibers is formed in multiple layers, and needling is performed. After carrying out lamination of a plurality of integrated needle mats integrated to obtain a preform, the preform is supplied to a double belt press to be heated, pressurized and cooled to maintain the impregnated and solidified state of the thermoplastic resin film in the reinforcing fiber layer. Easily impregnated thermoplastic composite, characterized in that.
According to claim 5, The thickness of the reinforcing fiber layer is obtained by using the impregnation thickness (h) of Equation 1,

(1)
v = volumetric flux or superficial velocity [m / s], K = melt permeation coefficient of the fiber tissue [m ² ], ΔP = pressure received through the fiber [Pa],

= Easily impregnated thermoplastic composite, characterized in that the viscosity [Pa.s] of the thermoplastic resin.
The method of claim 6, wherein the molten resin transmission coefficient (K) is obtained using Equation 2,

(2)
and d is the diameter of the fiber yarn, e is the porosity or porosity of the fiber mat.

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