阅读说明：本技术 一种低收缩率的耐热pvc木塑装饰板及制备方法 (Low-shrinkage heat-resistant PVC (polyvinyl chloride) wood-plastic decorative plate and preparation method thereof ) 是由 陈庆 昝航 曾军堂 于 2019-11-18 设计创作，主要内容包括：本发明提出一种低收缩率的耐热PVC木塑装饰板及制备方法,所述木塑装饰板是由植物秸秆纤维经预处理后,依次与硝酸溶液及氢氧化钠溶液混合加热,得到微孔秸秆纤维,然后反复交替浸入可溶性钙盐溶液及可溶性硅酸盐溶液中,得到表面具有硅酸钙硬质壳层的改性秸秆纤维,接着与聚氯乙烯、木粉、增塑剂、硅烷偶联剂混料,再经双螺杆挤出机成型而制得。本发明提供的方法预处理的秸秆纤维制得的木塑装饰板耐热性能更优异,并且极大地降低了木塑板的收缩率,并且赋予了木塑板强度高,防开裂,防翘曲等特点,同时秸秆纤维的处理方法简单易操作。(The invention provides a heat-resistant PVC (polyvinyl chloride) wood-plastic decorative plate with low shrinkage and a preparation method thereof. The wood-plastic decorative board prepared from the straw fibers pretreated by the method provided by the invention has more excellent heat resistance, the shrinkage rate of the wood-plastic board is greatly reduced, the wood-plastic board is endowed with the characteristics of high strength, cracking resistance, warping resistance and the like, and meanwhile, the treatment method of the straw fibers is simple and easy to operate.)

1. the heat-resistant PVC wood-plastic decorative board with low shrinkage rate is characterized in that the wood-plastic decorative board is prepared by pretreating plant straw fibers, sequentially mixing and heating the pretreated plant straw fibers with a nitric acid solution and a sodium hydroxide solution to obtain microporous straw fibers, repeatedly and alternately immersing the microporous straw fibers into a soluble calcium salt solution and a soluble silicate solution to obtain modified straw fibers with calcium silicate hard shells on the surfaces, mixing the modified straw fibers with polyvinyl chloride, maleic anhydride grafted polyethylene, wood powder, a plasticizer and a silane coupling agent, and molding the mixture by a double-screw extruder.

2. The heat-resistant PVC wood-plastic decorative board with low shrinkage rate according to claim 1, wherein the plant straw fiber is one or a combination of more than two of wheat straw fiber, rice straw fiber, corn straw fiber, sorghum straw fiber, sugarcane straw fiber, rape straw fiber and cotton straw fiber; the soluble calcium salt is calcium nitrate; the soluble silicate is one of sodium silicate and potassium silicate; the plasticizer is one or the combination of more than two of dioctyl phthalate and dibutyl phthalate; the silane coupling agent is one or the combination of more than two of kh540, kh550, kh560, kh570 and kh 792.

3. The heat-resistant PVC wood-plastic decorative board with low shrinkage according to claim 1, wherein the mass concentration of the nitric acid solution is 3%; the mass concentration of the sodium hydroxide solution is 3 percent; the mass concentration of the soluble calcium salt solution is 5-8%; the mass concentration of the soluble silicate solution is 10-15%.

4. The preparation method of the heat-resistant PVC wood-plastic decorative board with low shrinkage rate as claimed in any one of claims 1 to 3, which is characterized in that the specific preparation method is as follows:

(1) cutting plant straw fibers into small segments, washing, crushing, performing microwave treatment for 30-60min to obtain pretreated straws, mixing with a nitric acid solution, heating in a water bath at 85 ℃ for 60-90min, performing suction filtration and cleaning until filtrate is neutral, mixing with a sodium hydroxide solution, heating in a water bath at 85 ℃ for 60-90min, performing suction filtration and cleaning until filtrate is neutral, and drying at 60 ℃ to obtain straw fibers with a rough porous structure, namely microporous straw fibers for later use;

(2) immersing the microporous straw fiber prepared in the step (1) into a soluble calcium salt solution to enable the soluble calcium salt solution to fully permeate into micropores of the straw fiber, taking out after 30-60min, immersing into a soluble silicate solution, taking out after 30-60min, repeating the operation for 3-5 times, then carrying out solid-liquid separation, and drying at 60 ℃ to obtain the modified straw fiber with a calcium silicate hard shell layer on the surface for later use;

(3) conveying polyvinyl chloride, maleic anhydride grafted polyethylene, hard shell modified straw fiber, wood powder, plasticizer and silane coupling agent into a mixer together, mixing for 30-60min under the condition that the rotation speed is 100-plus-200 rpm, transferring the mixed material into a double-screw extruder, and performing die extrusion molding at 160-plus-185 ℃ to obtain the low-shrinkage PVC wood-plastic decorative plate.

5. The preparation method of the heat-resistant PVC wood-plastic decorative board with low shrinkage according to claim 4, wherein in the step (1), the mixing mass ratio of the straw fiber to the nitric acid solution is 1:6, and the mixing mass ratio of the straw fiber to the sodium hydroxide solution is 1: 6.

6. The preparation method of the heat-resistant PVC wood-plastic decorative board with low shrinkage according to claim 4, wherein in the step (2), the mixing mass ratio of the microporous straw fibers to the soluble calcium salt solution is 1:4, and the mixing mass ratio of the microporous straw fibers to the soluble silicate solution is 1: 4.

7. The preparation method of the heat-resistant PVC wood-plastic decorative board with the low shrinkage rate according to claim 4, wherein in the step (3), the mixing mass ratio of polyvinyl chloride, maleic anhydride grafted polyethylene, the hard shell layer modified straw fiber, wood powder, the plasticizer and the silane coupling agent is 30-40:10-15:15-20:25-30:12-18: 0.5-2.

Technical Field

The invention relates to the technical field of wood-plastic composite materials, in particular to a heat-resistant PVC wood-plastic decorative plate with low shrinkage and a preparation method thereof.

Background

The wood-plastic composite board is a high-tech green environment-friendly novel decorative material which is mainly prepared by uniformly mixing wood (wood cellulose and plant cellulose) as a base material, a thermoplastic high polymer material (plastic), a processing aid and the like, and then heating and extruding the mixture by using a die device, has the performance and characteristics of both wood and plastic, and is a novel composite material capable of replacing the wood and the plastic. The wood-plastic material has the advantages of biodegradability, reduction of solid wastes, excellent mechanical property, aging resistance, solid wood texture and the like, and is widely applied to outdoor garden landscapes and indoor decorative materials.

Among the wood-plastic composite boards, wood-plastic decorative boards are widely concerned as a novel environment-friendly wood-plastic composite product. The wood-plastic decorative plate is generally spliced and laid in a block shape. The joint of two pieces of floor boards is generally a buckle type structure, and the joint is provided with an interface, so that the joint is required to lock the buckle on four sides when being installed, and the installation strength is high when the floor boards are assembled in large scale.

In addition, because the common wood-plastic composite board is prepared by mixing wood and plastic, when the board is pressed strongly, the board is easy to deform and warp under stress. In addition, as the foaming agent is adopted in the raw materials of the wood-plastic floor, the shrinkage rate and the expansion rate are high, and the stability needs to be improved; in addition, the straw fiber and the resin matrix have poor bonding property, the pretreatment process is complex, and the cost is high. Therefore, research on novel high-performance wood-plastic decorative plates is increasing.

The Chinese patent application No. 201710313497.6 discloses a PVC wood-plastic composite decorative board, which is prepared from the following components: PVC resin, butyl rubber, modified polyformaldehyde/low-density polyethylene copolymer, glass fiber, light calcium carbonate, wood powder, PVC auxiliary agent, PVC reinforcing agent and silane coupling agent; the wood-plastic composite decorative board prepared by the invention can reduce the density of the composite material, reduce the production cost, and simultaneously can avoid the crack tip of the wood-plastic composite material, prevent the crack from expanding and improve the impact resistance and toughness of the wood-plastic composite material through the synergistic effect of the PVC auxiliary agent and the modified polyformaldehyde/low-density polyethylene copolymer. The Chinese invention patent application number 201610533561.7 discloses a modified straw/PP wood-plastic composite board and a processing method thereof, which is characterized by comprising the following components by mass ratio, 38-43 parts of modified wheat straw, 40-45 parts of polypropylene and 1-15 parts of coupling agent; the invention takes wheat straw fiber, waste polypropylene (PP) plastic film, KH550 silane coupling agent, acetic acid solution and ethanol solution as raw materials, and prepares the straw wood-plastic composite board through the working procedures of mixing and stirring the materials, paving and forming, hot-pressing and curing, drying and curing and the like.

In order to solve the problems of large shrinkage, low strength, easy warping and the like of the traditional wood-plastic composite board, a novel wood-plastic composite decorative board is necessary to be provided, and further the comprehensive performance of the wood-plastic composite board is effectively improved.

Disclosure of Invention

Aiming at the defects that the wood-plastic decorative plate in the prior art has large shrinkage rate, is easy to deform and warp under strong pressure, has a complex traditional straw fiber pretreatment process and the like, the invention provides the heat-resistant PVC wood-plastic decorative plate with low shrinkage rate and the preparation method thereof, so that the shrinkage rate of the wood-plastic plate is greatly reduced, and the wood-plastic decorative plate has the characteristics of high strength, cracking resistance, warping resistance and the like.

In order to solve the problems, the invention adopts the following technical scheme:

a heat-resistant PVC wood-plastic decorative plate with low shrinkage rate is prepared by pretreating plant straw fibers, mixing the pretreated plant straw fibers with a nitric acid solution and a sodium hydroxide solution in sequence, heating to obtain microporous straw fibers, repeatedly and alternately immersing the microporous straw fibers in a soluble calcium salt solution and a soluble silicate solution to obtain modified straw fibers with a calcium silicate hard shell layer on the surface, mixing the modified straw fibers with polyvinyl chloride, maleic anhydride grafted polyethylene, wood powder, a plasticizer and a silane coupling agent, and molding the mixture by a double-screw extruder.

Preferably, the plant straw fiber is one or a combination of more than two of wheat straw fiber, rice straw fiber, corn straw fiber, sorghum straw fiber, sugarcane straw fiber, rape straw fiber and cotton straw fiber.

Preferably, the soluble calcium salt is calcium nitrate.

Preferably, the soluble silicate is one of sodium silicate and potassium silicate.

Preferably, the plasticizer is one or a combination of more than two of dioctyl phthalate and dibutyl phthalate.

Preferably, the silane coupling agent is one or a combination of two or more of kh540, kh550, kh560, kh570 and kh 792.

Preferably, the mass concentration of the nitric acid solution is 3%.

Preferably, the mass concentration of the sodium hydroxide solution is 3%.

Preferably, the mass concentration of the soluble calcium salt solution is 5-8%.

Preferably, the mass concentration of the soluble silicate solution is 10-15%.

The invention also provides a preparation method of the heat-resistant PVC wood-plastic decorative board with low shrinkage, which comprises the following steps:

(1) cutting plant straw fibers into small segments, washing, crushing, performing microwave treatment for 30-60min to obtain pretreated straws, mixing with a nitric acid solution, heating in a water bath at 85 ℃ for 60-90min, performing suction filtration and cleaning until filtrate is neutral, mixing with a sodium hydroxide solution, heating in a water bath at 85 ℃ for 60-90min, performing suction filtration and cleaning until filtrate is neutral, and drying at 60 ℃ to obtain straw fibers with a rough porous structure, namely microporous straw fibers for later use;

(2) immersing the microporous straw fiber prepared in the step (1) into a soluble calcium salt solution to enable the soluble calcium salt solution to fully permeate into micropores of the straw fiber, taking out after 30-60min, immersing into a soluble silicate solution, taking out after 30-60min, repeating the operation for 3-5 times, then carrying out solid-liquid separation, and drying at 60 ℃ to obtain the modified straw fiber with a calcium silicate hard shell layer on the surface for later use;

(3) conveying polyvinyl chloride, maleic anhydride grafted polyethylene, hard shell modified straw fiber, wood powder, plasticizer and silane coupling agent into a mixer together, mixing for 30-60min under the condition that the rotation speed is 100-plus-200 rpm, transferring the mixed material into a double-screw extruder, and performing die extrusion molding at 160-plus-185 ℃ to obtain the low-shrinkage PVC wood-plastic decorative plate.

Preferably, in the step (1), the mixing mass ratio of the straw fiber to the nitric acid solution is 1:6, and the mixing mass ratio of the straw fiber to the sodium hydroxide solution is 1: 6.

Preferably, in the step (2), the mixing mass ratio of the microporous straw fibers to the soluble calcium salt solution is 1:4, and the mixing mass ratio of the microporous straw fibers to the soluble silicate solution is 1: 4.

Preferably, in the step (3), the mixing mass ratio of the polyvinyl chloride, the maleic anhydride grafted polyethylene, the hard shell modified straw fiber, the wood powder, the foaming agent, the foaming stabilizer, the plasticizer and the silane coupling agent is 30-40:10-15:15-20:25-30:12-18: 0.5-2.

According to the invention, the plant straw fiber is subjected to microwave treatment, so that the water in the silicon cells on the surface layer of the straw is rapidly expanded, internal pressure is instantly generated in the silicon cells and the subelement cells on the surface layer of the straw, the silicon cells and the subelement cells on the surface layer of the straw fiber are partially or completely destroyed, and the compact layer on the surface layer of the straw is loosened due to the disintegration of the cells.

Further, the plant straw fiber after microwave treatment is subjected to acid-base treatment in sequence, so that a rough porous structure is formed on the surface of the straw fiber. The concentration of the acid liquor and the alkali liquor in the acid-alkali treatment must be controlled in a lower range, otherwise, a large amount of straw fibers can be damaged, so that the acid liquor in the method selects a nitric acid solution with the mass concentration of 3%, and the alkali liquor selects a sodium hydroxide solution with the mass concentration of 3%.

Furthermore, the straw fibers with rough porous structures on the surfaces after microwave treatment and acid-base treatment are sequentially immersed into a soluble calcium salt solution and a soluble silicate solution for secondary treatment, the porous structures on the surfaces of the straw fibers fully adsorb the soluble calcium salt and the soluble silicate, and simultaneously, chemical reaction is carried out to generate calcium silicate on the surfaces of the straw fibers in situ to form a calcium silicate hard shell layer, so that the strength of the straw fibers is greatly improved, and finally, the hard shell layer modified straw fibers are mixed with polyvinyl chloride and maleic anhydride grafted polyethylene for extrusion, so that the wood-plastic decorative board with high strength, good heat resistance and low shrinkage rate can be obtained.

The prior wood-plastic decorative board has the defects of large shrinkage, low strength, poor heat resistance, easy deformation and warpage when being pressed strongly, complex straw fiber pretreatment process and the like, and limits the application thereof. In view of the above, the invention provides a heat-resistant PVC wood-plastic decorative board with low shrinkage and a preparation method thereof, and the technical points are as follows: cutting plant straw fibers into small sections, washing, crushing, and performing microwave treatment to obtain pretreated straws; mixing with nitric acid solution, heating in water bath, and filtering and cleaning until the filtrate is neutral; mixing with sodium hydroxide solution, heating in water bath, filtering, cleaning until the filtrate is neutral, and oven drying to obtain straw fiber with coarse porous structure; soaking the microporous straw fiber into a soluble calcium salt solution to enable the soluble calcium salt solution to fully permeate into micropores of the straw fiber, taking out, soaking into a soluble silicate solution, taking out, repeating the operation for 3-5 times to obtain modified straw fiber with a calcium silicate hard shell layer on the surface, then carrying out solid-liquid separation, and drying the coated modified straw fiber for later use; conveying polyvinyl chloride, maleic anhydride grafted polyethylene, hard shell modified straw fiber, wood powder, a plasticizer and a silane coupling agent into a mixer together, mixing, transferring into a double-screw extruder, and carrying out extrusion molding by using a die to obtain the low-shrinkage wood-plastic decorative plate. The wood-plastic decorative plate prepared from the straw fibers pretreated by the method provided by the invention has more excellent heat resistance, the shrinkage rate of the wood-plastic plate is greatly reduced by coating the straws with the in-situ calcium silicate, the wood-plastic plate has the characteristics of high strength, cracking resistance, warping resistance and the like, and the treatment method is simple and easy to operate.

Compared with the prior art, the invention provides the heat-resistant PVC wood-plastic decorative board with low shrinkage and the preparation method thereof, and the outstanding characteristics and excellent effects are as follows:

1. the straw fiber is pretreated by acid and alkali to form a rough porous structure on the surface of the straw fiber, then secondary treatment is sequentially carried out in soluble calcium salt and soluble silicate solution, and a calcium silicate hard shell layer is formed on the surface of the straw fiber through reaction.

2. The wood-plastic decorative board prepared from the straw fibers pretreated by the method disclosed by the invention has more excellent heat resistance, the shrinkage rate of the wood-plastic board is greatly reduced, and the wood-plastic board has the characteristics of high strength, cracking resistance, warping resistance and the like.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.