JP3320888B2 - Manufacturing method of lightweight stampable sheet with excellent mechanical strength - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a lightweight stampable sheet having excellent mechanical strength and useful as an interior material for automobiles such as ceiling materials and door trims.

[0002]

2. Description of the Related Art As a method for producing a lightweight stampable sheet, a papermaking method is known. This papermaking method has a length of 6
Dispersing a glass fiber for reinforcement of 50 mm and a granular thermoplastic resin in a surfactant-containing aqueous medium containing air microbubbles,
A web is prepared by shaping the dispersion with a porous support, and heat and pressure are applied to the web to obtain a solidified dense sheet (hereinafter sometimes referred to as a consolidation sheet). When the consolidation sheet is heated to a temperature equal to or higher than the melting point of the thermoplastic resin and the resin is melted, the consolidation sheet expands from its original thickness due to the glass fiber spring bag. The expanded sheet is placed on a mold and the required shape is obtained by compression molding. By adjusting the clearance of the mold during compression molding, a lightweight stampable sheet having a smaller density than the consolidator sheet can be obtained. This technology is known
No. 8423.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a method for producing a lightweight stampable sheet for a consolidation sheet obtained by a papermaking method. Since the rigidity of a flat plate such as a panel is proportional to (elastic modulus) × (thickness) ³ , it is advantageous to increase the plate thickness in order to increase the rigidity of a component. The lightweight stampable sheet utilizes the expansion of a glass fiber by a spring bag when the matrix resin is heated to a temperature equal to or higher than the melting point, and is suitable for increasing the rigidity of a flat plate.

[0004] However, the surface of the conventional lightweight stampable sheet obtained by the papermaking method has raised the glass fibers, and the rigidity has not been sufficiently improved. As a means for remedying this drawback, there is known a method in which a layer having a high elastic modulus is arranged on the front and back of a flat plate (a sandwich structure).
As a method of realizing a sandwich structure, (1) a method of laminating a film on the front and back surfaces of an expanded core material,
(2) A method in which a film is fused to the front and back surfaces of the unexpanded core material and then expanded (Yamaji et al., Forming, Vol.
Pp. 463-470, 1991), and (3) a method of increasing the glass fiber content on the front and back surfaces (Japanese Patent Publication No. 2-48423).

However, a method of laminating a film is not preferable because it complicates the process. In addition, in the method of increasing the glass fiber content on the front and back surfaces, when the skin of the stampable sheet is simultaneously bonded, a decrease in adhesiveness is inevitable.
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide an industrially easy manufacturing method of a lightweight stampable sheet having excellent bending characteristics and surface flatness.

[0006]

According to the present invention, a dispersion liquid is prepared by dispersing a reinforcing glass fiber and a granular matrix resin in a surfactant-containing aqueous medium in which air microbubbles are dispersed. A web is produced by making it on a porous support, and the web is heated, and while the matrix resin constituting the web is molten, the web is heated to between 1.5 mm or less of the theoretical thickness between hot plates. This is a method for producing a lightweight stampable sheet having excellent mechanical strength, wherein the sheet is immediately expanded between cooling boards to a predetermined thickness after being compressed.

The above-mentioned hot plate and cooling plate may be a thick plate such as a mere steel plate, a mold, or a roll. The theoretical thickness (t ₀ ) is defined as follows. t ₀ = G × {(W _m / _{r m} ) + (W _r / _{r r} )} / 10
0 Here, G: the basis weight of the sheet (g / m ² ) W _m : the weight fraction of the matrix W _r : the weight fraction of the glass fiber ρ _m : the density of the matrix ρ _r : the density of the glass fiber

[0008]

The operation of the present invention will be described below in detail. A feature of the present invention is that the web is compressed and expanded while the matrix resin is molten. By sufficiently compressing the preheated melted web, the sheet is uniformly filled with the matrix resin. This sheet is immediately inserted between cooling plates such as a mold whose clearance is adjusted to a desired product thickness by a spacer. At this time, since the surface cools quickly, it solidifies while maintaining the state of the compressed sheet. That is, a smooth surface state without holes is obtained. On the other hand, since the cooling of the inside is delayed, the inside is inflated by the glass fiber spring bag.

Therefore, the sheet manufactured by the method of the present invention has a sandwich structure with a smooth surface and a high flexural modulus. As described above, in the present invention, the web needs to be compressed while the matrix resin is molten. The thickness when compressed is the theoretical thickness (t ₀ )
Limited to 1.5 times or less. Preferably the theoretical thickness (t ₀ )
1.3 times or less. The thickness when compressed is the theoretical thickness (t ₀ )
If it is more than 1.5 times, the sheet surface after expansion will not be smooth and the elastic modulus will not be high.

[0010] The temperature of the hot platen itself is preferably 170 to 230 ° C. Particularly preferred is 190 to 210 ° C. The thickness is controlled using a spacer or the like. The required pressure at this time is
Although it depends on the basis weight and glass fiber content, it is usually 1-50kg
f / cm ² . The method of pressing the sheet includes press pressing and roll pressing, and is not particularly limited.

[0011] The temperature of the cooling plate such as a mold may be lower than the freezing point of the thermoplastic resin. The temperature is usually from room temperature to 60 ° C. from the viewpoint of handling properties and productivity. The molding pressure is the basis weight of the sheet,
Depending on the glass fiber content and product shape, usually
0.1-100 kgf / cm ² . Excessive pressure will break the glass fibers. The thickness of the lightweight stampable sheet is controlled by the clearance of the mold. The web is expanded by a glass fiber spring bag when the matrix resin is melted, and the expansion ratio is usually 1.1 to 10 times. In order to increase the rigidity of the sheet, the thickness of the sheet should be the theoretical thickness (t ₀ )
Larger than is better.

Regarding the reinforcing glass fiber In order to obtain a sufficient reinforcing effect and to ensure fluidity during molding, the length of the fiber is preferably 6 to 50 mm. More preferably, it is 10 to 26 mm. If the fiber is too long, the fluidity during molding is reduced, the glass fiber is not sufficiently opened in the papermaking process, the expansion is uneven, and the effect of springback is small. If it is too short, sufficient reinforcement effect cannot be obtained,
It is easy to break the paper in the papermaking process.

The diameter of the glass fiber is preferably 5 to 30 μm in order to ensure the reinforcing effect and the expanding effect of the glass fiber. More preferably, it is 10 to 25 μm. If the fiber diameter is small, sufficient expansion cannot be obtained during heating. If the fiber diameter is too large, a sufficient reinforcing effect cannot be obtained, and a feeling of pain occurs during handling. In the lightweight stampable sheet, the weight ratio of the reinforcing glass fiber to the matrix resin (glass fiber / resin) is used so as to be 20/80 to 70/30. Insufficient blend of glass fiber has little reinforcing effect,
Poor swelling. Excessive use of glass fibers also makes it difficult for the matrix resin to uniformly impregnate the glass fiber joints, resulting in reduced strength.

The surface of the reinforcing glass fiber is treated with a silane coupling agent and a sizing agent as necessary. The silane coupling agent is for improving the wettability and the adhesiveness, and the sizing agent is for controlling the opened state of the glass fiber. As the silane coupling agent, vinyl silane type, amino silane type, epoxy silane type, methacryl silane type, chlorosilane type, mercapton silane type, and the like can be used. Among them, aminosilane-based and epoxysilane-based are preferred. The method of treating the silane coupling agent into the glass fibers can be performed by a known method such as a spray method of spraying an aqueous solution of the silane coupling agent while mixing the glass fibers, or immersion in an aqueous solution of the silane coupling agent. The amount of the silane coupling agent is preferably 0.001 to 0.3% by weight based on the glass fiber. More preferably, it is 0.005 to 0.2 wt%. If it is less than 0.001 wt%, the improvement in strength is small.

In order to improve the strength and expandability of the lightweight stampable sheet, it is desirable to open the glass fibers into single fibers. For this purpose, the reinforcing glass fibers are treated with a water-soluble sizing agent. Examples of these sizing agents include a polyethylene oxide type and a polyvinyl alcohol type.
The amount of the sizing agent is preferably 0.03 to 0.3% by weight based on the glass fiber. More preferably, it is 0.05 to 0.2 wt%. 0.3wt
%, It becomes difficult to open in the papermaking process.

Matrix resin The matrix resin that can be used in the present invention is preferably a thermoplastic resin, such as polyolefin such as polyethylene and polypropylene, polystyrene, polyethylene terephthalate, polycarbonate, polyamide, polyacetal, and the like.
Polyvinyl chloride and the like, and copolymers, graft compounds and blends containing these resins as main components, such as ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene-acrylonitrile copolymer, etc. Is mentioned. Among them, polypropylene is preferred.

The average molecular weight of the matrix resin is from 50,000 to
700000 is preferred. If it is less than 50,000, the melt viscosity is low and the wettability to the glass fiber is good, but the mechanical properties of the lightweight stampable sheet deteriorate because the resin becomes brittle. Further, the fluidity is reduced. In order to improve the adhesiveness between the resin and the glass fiber, a resin obtained by modifying the matrix resin with a compound such as acid or epoxy can be used in combination. For polypropylene, maleic acid,
Those which can be modified with maleic anhydride, acrylic acid, or the like, and in which the modifying group is an acid anhydride group or a carboxyl group are preferable. The weight average molecular weight of the modified resin is preferably 2,000 to 200,000. If it is less than 2000, the melt viscosity is low and the wettability and adhesion to glass fibers are improved, but the mechanical properties of the lightweight stampable sheet are reduced because the resin becomes brittle. Further, the fluidity is reduced. The amount of modifying group is 0.02-3.0
wt% [(weight of functional group / weight of matrix resin) x 1
00] is preferred. More preferably, it is 0.05 to 2.0 wt%. If it is less than 0.02% by weight, the adhesion to the silane coupling agent becomes insufficient, and the strength improvement is reduced. 3.0wt
%, The embrittlement of the matrix resin, the coloring of the sheet and the like are caused.

The particles of the thermoplastic resin used for the web may be particles after polymerization, or particles obtained by so-called chemical pulverization in which the resin in the form of pellets is mechanically pulverized or dissolved once in a solvent and then precipitated. Is also good. The particles of the thermoplastic resin preferably have a diameter of 50 to 2000 μm, more preferably 200 to 1000 μm. If the particle size is too large, it may be difficult to obtain a consolidation sheet in which the fibers are uniformly impregnated with the resin. On the other hand, if it is too small, the pressure loss increases in the dewatering step of web production,
Manufacturing troubles may occur.

When a matrix resin and a modified resin are used in combination, a web may be produced using the respective particles, or a material obtained by melt-kneading and pulverizing them in advance with an extruder or the like may be used. Method for Producing Web Chopped strands of glass fiber and thermoplastic resin particles are dispersed in a surfactant-containing aqueous solution in which fine air bubbles are dispersed. By dehydrating the dispersion through a porous support, a uniform web can be obtained.
The web is composed of glass fibers and a thermoplastic resin, and the particles of the thermoplastic resin are uniformly dispersed in the glass fibers. The web is dried at a temperature below the melting point of the matrix resin.

An antioxidant, a light stabilizer,
Additives such as metal deactivators, flame retardants, carbon black, and coloring agents can be contained. These additives and coloring agents can be contained in the consolidation sheet, for example, by being previously blended with the granular thermoplastic resin or added by spraying during the consolidation sheet manufacturing process.

The method of manufacturing the expansion plate The web manufactured as described above is heated to a temperature not lower than the melting point of the resin, and immediately after being compressed between the hot plates, is placed between the cooling plates to obtain a lightweight stamper having a predetermined thickness and density. Molded into a bull sheet. The heating temperature of the web is higher than the melting point of the thermoplastic resin and lower than the decomposition temperature. When the thermoplastic resin is polypropylene, the heating temperature is preferably 170 to 230 ° C. Particularly preferred is 190-210 ° C. The method of heating the web includes hot plate heating, far-infrared heating, ventilation heating, and the like, and is not particularly limited.

The compression ratio, pressure and the like of the web are as described above. Hereinafter, the present invention will be specifically described based on examples.

[0023]

【Example】

(Example 1) Polypropylene resin (weight average molecular weight 2000
00, average particle size 500 μm) 33.75 g and glass fiber chopped strand (length 13 mm, diameter 13 μm, aminosilane 0.00)
22.50 g of 5 wt%, polyethylene oxide-based sizing agent 0.05 wt%, convergence number 5000 / bundle) was stirred and foamed in 10 l of a 0.8 wt% aqueous solution of sodium dodecylbenzenesulfonate to prepare a dispersion. The dispersion is poured into a paper machine having a paper making area of 250 × 250 mm, suctioned and defoamed, and a basis weight of 900 g / m 2.
After producing the web No. ^2, the web was dried at 130 ° C. for 1 hour. Similarly, ^two more webs having a basis weight of 900 g / m ² were prepared. After laminating three webs (theoretical thickness 2.2mm), 200
Preheat to ℃, placed between the hot platen maintained at 200 ℃, 5kgf
/ Cm ² pressure (clearance 2.2mm: theoretical thickness
1.0 times). Next, placed between cooling boards at 25 ° C, 5kgf / cm
Compressed with a pressure of ² (clearance 6.6mm) and cooled, a lightweight stampable sheet (glass fiber 40wt%, basis weight 2700g /
m ² ) was obtained. The surface of the sheet was smooth and had no glass fiber raised, and the polypropylene resin was uniformly dispersed.

The density was calculated from the weight and thickness of the sheet.
The bulk density was 0.41 g / cm ³ . From sheet, JIS
According to K7055, a bending test piece was cut out and subjected to a three-point bending test to measure the bending strength. Table 1 shows the results. (Example 2) Same as in Example 1 and a basis weight of 900 g / m ²
3 webs were prepared. After laminating three webs (theoretical thickness 2.2 mm), preheat to 200 ° C, place between hot plates maintained at 200 ° C, and compress under a pressure of 5 kgf / cm ² (clearance 2.7 mm: 1.23 of theoretical thickness) Times). Next, it is placed between cooling boards at 25 ° C and compressed at a pressure of 5 kgf / cm ² (clearance 6.
6mm) cool and lightweight stampable sheet (glass fiber 40w)
t%, basis weight 2700 g / m ² ). The surface of the sheet was smooth and had no glass fiber raised, and the polypropylene resin was uniformly dispersed.

The density was calculated from the weight and thickness of the sheet.
The bulk density was 0.41 g / cm ³ . From sheet, JIS
According to K7055, a bending test piece was cut out and subjected to a three-point bending test to measure the bending strength. Table 1 shows the results. (Example 3) The basis weight was 900 g / m ^{2 in the same} manner as in Example 1.
3 webs were prepared. After laminating three webs (theoretical thickness 2.2 mm), preheat to 200 ° C., place between hot plates maintained at 200 ° C., and compress with a pressure of 5 kgf / cm ² (clearance 3.3 mm: 1 of theoretical thickness) .5 times). Next, it is placed between cooling boards at 25 ° C and compressed with a pressure of 5 kgf / cm ² (clearance
6.6mm) cooled, lightweight stampable sheet (glass fiber
40 wt% and a basis weight of 2700 g / m ² ) were obtained. The surface of the sheet was smooth and had no glass fiber raised, and the polypropylene resin was uniformly dispersed.

The density was calculated from the weight and thickness of the sheet.
The bulk density was 0.41 g / cm ³ . From sheet, JIS
According to K7055, a bending test piece was cut out and subjected to a three-point bending test to measure the bending strength. Table 1 shows the results. (Comparative Example 1) A basis weight of 900 g / m ^{2 in the same} manner as in Example 1.
3 webs were prepared. After laminating three webs (theoretical thickness 2.2 mm), preheat to 200 ° C, place between cooling boards at 25 ° C, and compress with a pressure of 5 kgf / cm ² (clearance 6.6 m
m) Cool. The surface of the obtained light-weight stampable sheet (glass fiber 40 wt%, basis weight 2700 g / m ² ) had glass fiber raised. The density was calculated from the weight and thickness of the sheet. The bulk density was 0.41 g / cm ³ . A bending test piece was cut out from the sheet according to JIS K7055, and a three-point bending test was performed to measure the bending strength. Table 1 shows the results.

(Comparative Example 2) Weight per unit area in the same manner as in Example 1.
Three 900 g / m ² webs were prepared. After laminating three webs (theoretical thickness 2.2mm), preheat at 200 ° C, place between hot plates at 200 ° C, and compress with 5kgf / cm ² pressure (clearance
4.4 mm: 2.0 times the theoretical thickness). Next, it is placed between cooling boards at 25 ° C and compressed with a pressure of 5 kgf / cm ² (clearance 6.6
mm) cooled and lightweight stampable sheet (glass fiber 40wt
%, A basis weight of 2700 g / m ² ).

The density was calculated from the weight and thickness of the sheet.
The bulk density was 0.41 g / cm ³ . From sheet, JIS
According to K7055, a bending test piece was cut out and subjected to a three-point bending test to measure the bending strength. The results are shown in Table 1 together with the observation of the surface condition of the sheet.

[0029]

[Table 1]

[0030]

According to the method of the present invention, a lightweight stampable sheet having a sandwich structure having high rigidity can be easily obtained industrially. Therefore, it can be advantageously used for automobile interior members requiring high rigidity, such as ceiling materials and door trims.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-238658 (JP, A) JP-A-58-104719 (JP, A) JP-A-56-11229 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B29B 11/16 B29B 15/10

Claims (1)

(57) [Claims] 1. A dispersion in which a reinforcing glass fiber and a particulate matrix resin are dispersed in a surfactant-containing aqueous medium in which air microbubbles are dispersed is prepared, and the dispersion is prepared on a porous support. After heating the web, compressing the web between hot plates to 1.5 times or less the theoretical thickness while the matrix resin composing the web is molten, and immediately between the cooling plates A method for producing a lightweight stampable sheet having excellent mechanical strength.