JPH09150415A - Manufacture of smc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain SMC excellent in impregnability or make a molding, which has no surface defect such as void, cavity or the like and favorable mechanical strength by a method wherein the bubbles in SMC, even to the fine ones, are removed equally and nearly perfectly. SOLUTION: At the manufacturing of SMC by infiltrating resin paste P containing thermosetting resin, inorganic filler, hardener, thickener or the like in the infiltrating process, resin paste P under the state being vibrated with vibrating oscillators 3a and 3b (such as eccentric shaft type oscillators) is infiltrated in reinforcing resin 9. Their vibration characteristics are the vibration frequency of 10-5,000Hz and the vibratory amplitude of 1-500μm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing SMC by impregnating a reinforcing fiber with a resin paste containing a thermosetting resin, and more particularly, to producing SMC in which bubbles in the SMC are greatly reduced. Regarding the method.

[0002]

2. Description of the Related Art Thermosetting resin molding material obtained by impregnating reinforcing fibers such as glass fibers with a resin paste obtained by adding a filler, a curing agent, a thickener, etc. to a thermosetting resin and forming it into a sheet shape. Is a sheet molding compound (SMC)
is called. SMC is mainly compression-molded and is widely used for large-sized molded articles such as housing equipment, transportation equipment, and industrial parts.

As one of the important factors in the quality of SMC,
Impregnating property can be mentioned. This is a measure of whether or not the reinforcing fiber is sufficiently wetted by the resin paste, and if the impregnation property is poor, not only voids and cavities are formed on the surface of the molded product, but also mechanical strength is lowered. The main cause of impairing the impregnation is the presence of air (hereinafter referred to as bubbles) contained in SMC. These bubbles may be contained in the raw material resin or reinforcing fiber, mixed in the resin paste mixing step, mixed in the SMC impregnation step, or the like. That is, in the SMC impregnation step, the resin paste is applied onto the carrier film, the reinforcing fibers cut into a certain length are scattered on the film, and the reinforcing fibers are sandwiched between the carrier films coated with the resin paste. The roll is pressure-impregnated, but bubbles are mixed during this pressure-impregnation.

Usually, as a means for improving the impregnating property,
The bearer belt method and the double mesh method are used in the pressure impregnation step in the SMC production, but none of these methods has completely removed the bubbles.

Therefore, in order to remove the bubbles, for example, in Japanese Patent Publication No. 6-57409, the bubbles in the SMC accumulated in front of the impregnating roller in the SMC impregnation step are treated by SM.
A method is disclosed in which an air vent that moves at a right angle to the traveling direction of C is moved in a transverse reciprocating manner while being in contact with the SMC to discharge from the side end of the SMC.

[0006]

However, the method described in the above publication is certainly effective for large bubbles in front of the impregnating roll, but is almost effective for fine bubbles in SMC. has no effect. The fine bubbles not only enter between the resin paste and the reinforcing fiber to impair the impregnation property, but also reduce the surface property and mechanical strength of the molded product manufactured from SMC.

The object of the present invention is to solve the problems of the prior art and to eliminate the air bubbles in the SMC uniformly and almost completely, thereby improving the impregnation property of S.
An object of the present invention is to provide a method for producing MC, that is, SMC which is free from surface defects such as voids and cavities and can be molded into a molded product having good mechanical strength.

[0008]

The method for producing SMC according to the present invention is a method for producing SMC (sheet molding compound) by impregnating reinforcing fibers with a resin paste containing a thermosetting resin. At
It is characterized in that the reinforcing fiber is impregnated with the resin paste while applying vibration. The resin paste is usually
In addition to the thermosetting resin, it contains an inorganic filler, a curing agent, a thickener, and the like. Hereinafter, the present invention will be described in detail.

First, an outline of the SMC manufacturing process will be described. The manufacturing process of SMC usually includes three steps of a mixing step, an impregnation step and an aging step. The mixing step is a step of kneading a raw material other than the reinforcing fibers such as a thermosetting resin, an inorganic filler, a curing agent and a thickener to obtain a resin paste. In the impregnation step, a certain amount of this resin paste is applied onto a carrier film, and reinforcing fibers such as glass fibers cut into a certain length are spread on the film, while the carrier film coated with the resin paste is It is a series of steps of placing on top, impregnating them with a sandwiching roll, and impregnating the obtained sheet, and wrapping with a polyethylene film or the like so that polymerizable monomers such as styrene do not volatilize. In the aging step, the wound SMC is usually used for half a day to 2 days,
This is a step of storing in a temperature-controlled aging chamber at 25 to 50 ° C. and increasing the viscosity to a predetermined viscosity.

In the present invention, the impregnation method is not particularly limited, but it is a conventional conveyor belt impregnation method (a method of impregnating by a compaction roll sandwiching a conveyor belt and pressure bonding with an air cylinder) or double. Mesh belt impregnation method (rolls arranged alternately top and bottom and special knitting
By combining with Dual-Wire-Mesh-Belt, the thickness of the sheet, the method of impregnating by utilizing the peripheral speed difference generated between the upper and lower sides) and the like can be mentioned.

The conveyor belt impregnation method will be described with reference to the drawings. That is, FIG. 1 shows an outline of a conveyor belt impregnation method, and SMC is obtained by being conveyed from the left side to the right side of the drawing by a conveyor belt (6). In FIG. 1, the resin paste (P) obtained in the mixing step is applied on the carrier film (4b) at a constant amount per unit area by the action of the doctor blade (5b),
The chopped strands (9) obtained by cutting the glass roving (8) into a certain length with a chopper (7) are scattered on the film (4b). On the other hand, the resin blade (P) above the conveyor belt (6), the doctor blade (5a)
Is applied to the carrier film (4a). This film (4a) is placed on the carrier film (4b) with the resin paste (P) facing downward, and thus the chopped strands sandwiched between the upper and lower carrier films (4a) and (4b). A resin paste (P) containing (9) is obtained and introduced into the pressure impregnation section. That is, the compaction roll (1
A) and (1b) are guided to a pressure impregnation section arranged in a pair of upper and lower sides, and sandwiched by compaction rolls (1a) and (1b) to perform pressure impregnation. In the present invention, the frame (2a) (2b) supporting the compaction rolls (1a) (1b) respectively, the vibration oscillator (3a) (3
b) is attached, and the vibration from the vibration oscillators (3a) (3b) is transmitted to the compaction rolls (1a) (1b). Therefore, the SMC has a compaction roll (1
a) It is impregnated under pressure while being vibrated by (1b).
The obtained sheet is wound up by a winding roll (10).

FIG. 2 is a vertical sectional view showing details of the sandwiching and pressing of the SMC by the compaction rolls (1a) (1b) in FIG. The air bubbles (A) in the SMC are discharged while being vibrated by the compaction rolls (1a) and (1b) while being pressurized, and are discharged from the end portion on the SMC side.

Next, the double mesh belt impregnation method will be described with reference to FIGS. That is, FIG.
FIG. 4 is a vertical sectional view of a pressure impregnated portion of the double mesh belt impregnation method, and FIG. 4 is a vertical sectional view showing details in the vicinity of the roll (12b) in FIG. In FIG.
The resin paste (P) containing chopped strands (9) sandwiched between the upper and lower carrier films (4a) and (4b) is guided to the pressure impregnation section and driven by rolls (12a) and (12b) arranged alternately in the upper and lower directions. The space between the pair of upper and lower double mesh belts (13a) and (13b) is pressed and impregnated by the thickness of the sheet and the peripheral speed difference generated between the upper and lower sides. In the present invention, the roll (12a) (12b)
The vibration oscillators (3a) and (3b) are attached to the frames (13a) and (13b) that respectively support the vibration oscillators (3a) and (3b).
It is designed to transmit the vibration from the roll to the rolls (12a) and (12b). Therefore, the SMC is pressure-impregnated while being vibrated by the rolls (12a) and (12b).

In any of the above methods, a vibration oscillator
Known materials can be used as (3a) and (3b).
That is, mechanical oscillating oscillators such as eccentric shaft type, cam / crank type, unbalanced weight type, electromagnetic oscillating oscillators such as electrodynamic exciter, and electro-hydraulic oscillating oscillators A machine or the like can be used.

For example, FIG. 5 shows an example in which the eccentric shaft type vibration oscillator is attached to the support frame (2b) of the compaction roll (1b) in the above-mentioned conveyor belt impregnation system. In FIG. 5, the bearing (22) having the eccentric rotation shaft (21) rotates, so that the casing
(23) vibrates horizontally and vertically. Then, this vertical vibration vibrates the vertical shaft (24), and the support frame (2
b) is vibrated.

As the vibration characteristics given to the pressure impregnated portion, the vibration frequency is usually 10 to 5000 Hz and the vibration amplitude is 1 to
The range is 500 μm. When the vibration frequency is less than 10 Hz, the effect of vibration does not sufficiently appear. Moreover, when the vibration frequency exceeds 5000 Hz, the SMC itself generates heat,
The curing phenomenon is likely to occur partially. The vibration frequency is preferably in the range of 250 to 3000 Hz in consideration of the balance between the effect of vibration in a short time and the effect on SMC. If the vibration amplitude is less than 1 μm, the effect of vibration does not sufficiently appear,
Further, if the vibration amplitude exceeds 500 μm, mechanical equipment may be adversely affected. Preferred vibration amplitude is 50-3
The range is 50 μm.

The direction of vibration may be vertical (in the thickness direction of the SMC), horizontal (in the SMC transport direction, a direction perpendicular to the transport direction), or three-dimensional, but three-dimensional vibration is more effective. Is.

Next, the resin paste and reinforcing fiber used in the present invention will be described.

The resin paste is generally a thermosetting resin,
It is composed of a filler, a curing agent, a thickener and the like.

As the thermosetting resin, for example, unsaturated polyester resin, vinyl ester resin, epoxy resin,
Phenol resin etc. can be mentioned. Among them, unsaturated polyesters and vinyl ester resins are preferable, and unsaturated polyester resins are particularly preferable because they have good thickening properties and moldability.

The unsaturated polyester resin is an unsaturated polyester obtained by polycondensing an unsaturated dibasic acid, a glycol, and optionally a saturated dibasic acid, a polymerizable monomer, and a low shrinkage added if necessary. It is a mixture of thermoplastic resins for chemical conversion.

As the unsaturated dibasic acid, for example, maleic anhydride, fumaric acid, itaconic acid, citraconic acid and the like are used. Examples of the glycol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-butanediol,
1,4-butanediol, 1,6-hexanediol,
Examples thereof include bisphenol A, hydrogenated bisphenol A, ethylene oxide adduct of bisphenol A, neopentyl glycol and the like. Examples of the saturated dibasic acid include phthalic anhydride, orthophthalic acid, isophthalic acid,
Examples thereof include terephthalic acid, adipic acid, succinic acid, tetrachlorophthalic acid and het acid.

Examples of the polymerizable monomer include styrene, dichlorostyrene, vinyltoluene, vinyl acetate,
Methacrylic acid, methacrylic acid ester, acrylic acid, acrylic acid ester, diallyl phthalate and the like can be mentioned, but styrene is preferably used.

The thermoplastic resin for reducing the shrinkage includes, for example, polystyrene, polyvinyl acetate, polymethyl methacrylate, polyethylene, poly ε-caprolactone, saturated polyester, polyvinyl chloride, polybutadiene, polystyrene-acrylic acid copolymer. Examples thereof include polymers, polystyrene-polyvinyl acetate copolymers, ethylene-vinyl acetate copolymers, vinyl chloride-vinyl acetate copolymers and acrylonitrile-styrene copolymers.

The vinyl ester resin is a resin having a vinyl group at the terminal of an ester chain or an ether chain, and generally refers to an epoxy acrylate resin. The epoxy acrylate resin is an epoxy acrylate obtained by reacting an bisphenol-type or novolac-type epoxy resin with an unsaturated-basic acid such as acrylic acid or methacrylic acid, a polymerizable monomer, and a low-addition agent added as necessary. It is a mixture of a thermoplastic resin for shrinking. As the polymerizable monomer and the thermoplastic resin for reducing the shrinkage, which is added if necessary, the above-mentioned ones are used.

As the filler, calcium carbonate, aluminum hydroxide, calcium sulfate, glass powder, talc,
An inorganic filler such as mica is used. The particle size of the inorganic filler is generally 0.1 to 200 μm, preferably 0.1.
5 to 60 μm. If the particle size is smaller than 0.1 μm,
The composition has a high viscosity, is not sufficiently infiltrated with the reinforcing fiber, and bubbles are easily mixed in the material, and as a result, a cavity is likely to be formed in the molded product. On the other hand, if the particle size is larger than 200 μm,
When the specific surface area of the particles is small, the viscosity of the composition is small and the handleability is low. The amount of the filler added is 100 parts by weight of the thermosetting resin composition, whether one of the above fillers is used alone or two or more of them are used together. It is in the range of 50 to 350 parts by weight. It is preferably in the range of 60 to 300 parts by weight. If the addition amount is less than 50 parts by weight, the handling property of the material before molding is deteriorated. On the other hand, if the addition amount is more than 350 parts by weight, the viscosity will be significantly increased, it will be difficult to uniformly mix the filler and the resin, the cured product will be brittle, and the mechanical properties will be deteriorated.
In addition, the fluidity at the time of molding is reduced, the impregnability into the reinforcing fiber is reduced, and air bubbles are easily mixed in the material, and as a result, cavities are easily formed in the molded product. Here, 100 parts by weight of the thermosetting resin composition means a polymer (oligomer) component such as an unsaturated polyester resin and an epoxy acrylate, a polymerizable monomer, and a shrinkage agent which is added if necessary. The total amount of the thermoplastic resin and the thermoplastic resin is 100 parts by weight.

As the curing agent, tertiary butyl peroxyisobutyrate, tertiary butyl peroxy 2-ethylhexanoate, tertiary amyl peroxy 2-ethylhexanoate, 2,4,4-trimethylpentylper Oxy-2-ethylhexanoate, tert-butyl peroxypivalate, tert-butyl peroxybenzoate, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxy 3,5,5-trimethylhexanoate,
1,1-bis (tertiary butyl peroxy) 3,
Examples thereof include organic peroxides such as 3,5-trimethylcyclohexane, benzoyl peroxide, methyl ethyl ketone peroxide, and cumene hydroperoxide. The addition amount of the curing agent is generally the thermosetting resin composition 10
It is about 0.2 to 2.0 parts by weight with respect to 0 parts by weight.

Examples of the thickener include magnesium oxide, magnesium hydroxide, calcium oxide, zinc oxide and the like. The addition amount of the thickener is generally the thermosetting resin composition 1
It is about 0.2 to 3 parts by weight with respect to 00 parts by weight.

As the reinforcing fibers in the present invention, glass fibers, carbon fibers, asbestos fibers, whiskers, organic synthetic fibers, natural fibers and the like are used. Glass fiber is preferably used in terms of physical properties and price. In addition to the case where a fiber having a fixed length or continuous fibers is used as it is, a mat-shaped or cloth-shaped fiber is also used. For example, in the case of glass fiber,
A chopped strand obtained by cutting the strand into a certain length, a chopped strand mat in which the chopped strand is bonded with a binder to form a mat, and the like are used.
The fiber length of the fixed length is usually 1 to 80 mm, preferably 10 to 50 mm. If the fiber length is shorter than 1 mm, there is no reinforcing effect, while if it is longer than 80 mm, the viscosity increases and the moldability deteriorates. Further, the orientation of the fibers in the unsaturated polyester resin composition, in addition to random orientation,
Those arranged in one direction, those arranged in an X shape, and the like are used.

The amount of the reinforcing fibers is in the range of 2 to 40% by weight, preferably 3 to 35% by weight, based on the entire thermosetting resin paste (SMC) containing the reinforcing fibers. When the amount of the reinforcing fiber is less than 2% by weight, the handling property of the material is deteriorated, and there is no reinforcing effect, and the molded product is easily cracked and bent. On the other hand, when the amount of the reinforcing fibers is more than 40% by weight, the viscosity increases and the fluidity deteriorates.

In the present invention, the resin paste usually further contains a release agent, a pigment and the like in addition to the above-mentioned thermosetting resin, filler, curing agent and thickener. Examples of the release agent include zinc stearate and calcium stearate.

The sheet thickness of the SMC manufactured according to the present invention is generally about 1 to 8 mm.

According to the SMC manufacturing method of the present invention, the reinforcing fiber is impregnated with the resin paste in the impregnation step while vibrating, that is, the SMC is vibrated during pressure impregnation. As a result, the resin viscosity is reduced and the wettability to the reinforcing fiber is improved, and even the fine bubbles in the resin paste combine with neighboring fine bubbles due to vibration and change into large bubbles, and then SMC.
It is discharged to the outside. Further, the air bubbles clinging to the reinforcing fibers move from the reinforcing fibers into the resin paste by vibration and are discharged to the outside of the SMC by the same mechanism as described above.

Due to the above-mentioned actions, the SMC obtained by the method of the present invention completely eliminates fine bubbles,
It has very good impregnation property. Therefore, the molded product obtained from it also has excellent surface properties and mechanical properties.

[0035]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples.

Example 1 100 parts by weight of an unsaturated polyester resin obtained by dissolving 40 parts by weight of an unsaturated polyester and 10 parts by weight of polystyrene in 50 parts by weight of a styrene monomer, 140 parts by weight of calcium carbonate, and tertiary butyl par 1.5 parts by weight of oxybenzoate, 5 parts by weight of zinc stearate, and 0.7 parts by weight of magnesium oxide were added and mixed with a stirrer to obtain a resin paste. Next, S
This resin paste was loaded into the upper and lower doctor blades of the MC manufacturing device (the device of the conveyor belt impregnation system shown in FIG. 1), and the roving chopper was added so that the glass fiber (25 mm length) content in the SMC was 25% by weight. Vibration oscillator (Eccentric shaft oscillator shown in Fig. 5)
To a compaction roll with a vibration frequency of 260 Hz and an amplitude of 300 μm in the vertical direction, and a line speed of 15
SMC was produced at m / min and subsequently aged at 40 ° C. for 24 hours. As the evaluation of the obtained SMC, bubble ratio measurement and visual evaluation were performed.

Next, the obtained SMC was molded into a mini-bath-shaped mold (width 3
50 mm × length 600 mm × height 270 mm), and compression-molded at a molding pressure of 100 kg / cm ² and a pressure time of 4 minutes using a 300-ton press machine manufactured by Kawasaki Yuko Co., Ltd.
A molded product was obtained. As the evaluation of the obtained molded product, bending strength (bottom surface, side surface) and surface property were evaluated.

The SMC bubble ratio measurement, visual evaluation, bending strength measurement of the molded product, and surface property evaluation were performed as follows. <Measurement of Bubble Ratio> Measurement was performed 3 times in accordance with JIS K 7053, and the average value was taken as the bubble ratio (%). <Visual Evaluation> The SMC was cut and the wet condition of the glass fiber and the resin inside the SMC was visually observed, and evaluated as ⊚: very good ∘: good Δ: somewhat poor x: poor <Measurement of Bending Strength> Each of the bottom surface and the side surface of the molded product was measured 5 times according to JIS K 69ll, and the average value was defined as the bending strength (MPa). <Surface property> The presence or absence of cavities, pinholes, and protruding glass fibers on the surface of the molded product was observed.

[Embodiment 2] As a vibration oscillator, Embodiment 1 is used.
An SMC and a molded product were manufactured in the same manner as in Example 1 except that an electromagnetic type oscillator was used in place of the eccentric shaft type oscillator described above, and vibration with a vibration frequency of 2500 Hz and an amplitude of 300 μm was applied, and their evaluation was performed. I did.

[Example 3] SMC and molded articles were produced and evaluated in the same manner as in Example 1 except that the amount of calcium carbonate was increased to 200 parts by weight.

Example 4 SMC and molded products were produced and evaluated in the same manner as in Example 1 except that the glass fiber content was increased to 40% by weight.

[Embodiment 5] The thickness of the SMC sheet is 5.0.
SMC and molded products were manufactured and evaluated in the same manner as in Example 1 except that the pressures of the upper and lower compaction rolls were set to be mm.

[Embodiment 6] SMC was carried out in the same manner as in Embodiment 1 except that the line speed of the SMC manufacturing apparatus was increased to 25 m / min.
MCs and molded products were manufactured and evaluated.

[Embodiment 7] FIG. 3 shows an SMC manufacturing apparatus.
Using the double mesh belt impregnation system shown in FIG. 3, SMC and molded products were manufactured in the same manner as in Example 1 except that the SMC sheet thickness was adjusted to 3.0 mm, and their evaluation was performed. It was

[Embodiment 8] Vibration frequency 9 Hz, amplitude 30
SMC and molded products were manufactured and evaluated in the same manner as in Example 1 except that vibration of 0 μm was applied.

[Comparative Example 1] Except that no vibration was applied,
SMC and molded products were manufactured in the same manner as in Example 1 and evaluated.

[Comparative Example 2] SMC and a molded article were produced and evaluated in the same manner as in Example 1 except that the amount of calcium carbonate was increased to 200 parts by weight and no vibration was applied.

[Comparative Example 3] An SMC and a molded product were produced and evaluated in the same manner as in Example 1 except that the glass fiber content was increased to 40% by weight and no vibration was applied.

[Comparative Example 4] The thickness of the SMC sheet was 5.0.
SMC and molded products were manufactured and evaluated in the same manner as in Example 1 except that the pressure of the upper and lower compaction rolls was set to be mm and vibration was not applied.

Table 1 shows a summary of the manufacturing conditions of Examples 1 to 8 and Comparative Examples 1 to 4 and the evaluation results of SMC and molded products.

[Table 1]

As shown in Table 1, the SMCs obtained in Examples 1 to 7, which were subjected to pressure impregnation while applying vibration, contained almost no bubbles and were excellent in impregnation property. It was The SMC obtained in Example 8 also had few bubbles. The molded products obtained by compression molding these SMCs were also very excellent in mechanical properties and surface properties. Comparative Examples 1 to 1 in which pressure impregnation was performed without applying vibration
The SMC obtained in No. 4 had a large bubble ratio and poor impregnability. Further, by comparing Example 3 with Comparative Example 2, comparing Example 4 with Comparative Example 3, comparing Example 5 with Comparative Example 4, and by applying vibration during pressure impregnation,
The addition amount of the filler and the glass fiber content can be increased, and the sheet thickness of the SMC can be increased.

[0052]

According to the method of the present invention, as described above,
By almost completely discharging even fine bubbles in the SMC, it is possible to manufacture an SMC having excellent impregnating properties. Therefore, from the SMC obtained by this method, it is possible to produce a molded article having very excellent surface properties and mechanical properties. Further, according to the present method, since the impregnating property of SMC is improved, it is possible to increase the amount of filler and the content of glass fiber. Therefore, the SMC obtained by this method
Further improvement in mechanical properties of molded articles manufactured from Further, since the sheet thickness of SMC can be increased, the number of charged sheets at the time of molding can be reduced. Furthermore, according to this method, the time efficiency of impregnation is also improved, so that the line speed of the SMC manufacturing apparatus can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a conveyor belt impregnation method.

FIG. 2 Compaction rolls (1a) (1b) in FIG.
FIG. 5 is a vertical cross-sectional view showing details of the sandwiching pressurization of SMC in FIG.

FIG. 3 is a vertical cross-sectional view of a pressure impregnation section of a double mesh belt impregnation method.

FIG. 4 is a vertical sectional view showing details in the vicinity of the roll (12b) in FIG.

5 is a view showing an example in which an eccentric shaft type vibration oscillator is attached to a support frame (2b) of the compaction roll (1b) in FIG.

[Explanation of symbols]

 (P) ... Resin paste (1a) (1b) ... Compaction roll (2a) (2b) ... Compaction roll support frame (3a) (3b) ... Vibration oscillator (4a) (4b) ... Carrier film (5a) ( 5b) ... Doctor blade (6) ... Conveyor belt (7) ... Chopper (8) ... Glass roving (9) ... Chopped strand (10) ... Winding roll (A) ... Air bubbles

Claims (1)

[Claims] 1. A method for producing an SMC (sheet molding compound) by impregnating a reinforcing fiber with a resin paste containing a thermosetting resin, wherein in the impregnating step, the reinforcing fiber is impregnated with the resin paste while vibrating. A method for manufacturing an SMC, comprising: