A white transparent plastic mulch film and its preparation method

Abstract

The present invention discloses a white transparent plastic mulch paper and a preparation method thereof, comprising the following steps: beating bleached softwood pulp or a mixed pulp of bleached softwood pulp and bleached hardwood pulp to a pulp with a beating degree of 85-95°SR; dissolving PVA in water and stirring at 85-100°C for 1-3 h to obtain a PVA solution; then adding the PVA solution and a papermaking aid to the pulp, fully mixing, defibering and then papermaking to obtain a base paper for the plastic mulch; the papermaking aid includes a dry strength agent, a wet strength agent, a sizing agent and a retention aid; coating one side of the base paper for the plastic mulch with polyamide polyamine epichlorohydrin resin, carnauba wax, polyurethane, waterborne acrylic resin or polyethylene wax, and coating the other side with epoxidized soybean oil, liquid paraffin, chlorinated paraffin, epoxy resin or polymethylhydrogensiloxane, and drying to obtain the product. This plastic mulch paper has a high visible light transmittance, strong wet strength and water vapor barrier performance, and can be used to replace white plastic mulch to solve environmental pollution problems caused by plastic mulch.

Description

Technical Field

[0001] The present invention belongs to the technical field of paper-based mulch films, and particularly relates to a white transparent mulch film paper and a preparation method thereof. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Mulching crops with plastic films has been a major technical measure in the development of agricultural production for a long time. White transparent plastic mulch films are the most commonly used ones when farmers lay them. They have various functions such as increasing soil temperature, maintaining environmental humidity, and promoting crop growth. Especially in the inland areas of North China, due to the large temperature difference between day and night, the use frequency of transparent mulch films is relatively high.

[0004] Over the years, the problem of emphasizing use over recycling in production activities has made the environmental pollution problem caused by waste mulch films increasingly serious. Mulch film paper uses plant pulp as the basic raw material, adds papermaking aids such as wet strength agents, preservatives, and transparent agents to the pulp, obtains the base paper through conventional papermaking processes, and then processes it to make the paper have the mechanical strength, light transmittance, hydrophobicity, heat preservation, temperature increase, moisture retention, and other functions required for laying mulch films. Compared with plastic mulch films, paper-based mulch films have the advantages of being biodegradable and having no environmental pollution. However, due to the light impermeability and hydrophilicity of plant fibers, most of the current mulch film papers still have problems such as poor light transmittance, low dry and wet strength, and poor hydrophobic and moisture-proof effects, which restrict the application of mulch film paper. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a white transparent mulch film paper and a preparation method thereof. This mulch film paper has a high visible light transmittance, strong wet strength, and water vapor barrier performance, and can be used to replace white plastic mulch films to solve environmental pollution problems caused by plastic mulch films.

[0006] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0007] In the first aspect, the present invention provides a preparation method of a white transparent mulch film paper, including the following steps:

[0008] Beating bleached softwood pulp or a mixed pulp of bleached softwood pulp and bleached hardwood pulp to a beating degree of 40 - 60°SR first, and then performing multiple grinding operations to obtain a pulp with a beating degree of 85 - 95°SR;

[0009] Dissolving polyvinyl alcohol (PVA) in water and stirring at 85 - 100°C for 1 - 3 h to obtain a 1 - 5 wt% PVA solution;

[0010] Then, 1%-2% of PVA (the solid content percentage of PVA relative to the mass of absolute dry pulp, the same below) and papermaking aids are added to the pulp, mixed thoroughly, defibered, and then sheeted to obtain the base paper for the plastic film; the papermaking aids include dry strength agent, wet strength agent, sizing agent, and retention aid;

[0011] On one side of the base paper for the plastic film, polyamide polyamine epichlorohydrin resin (PAE), carnauba wax, polyurethane, waterborne acrylic resin, or polyethylene wax is coated, and on the other side, epoxidized soybean oil, liquid paraffin, chlorinated paraffin, epoxy resin, or polymethylhydrogensiloxane is coated, and then dried to obtain the product.

[0012] In some embodiments, the concentration of polyamide polyamine epichlorohydrin resin is 1-5%, and the coating amount is 5-10 g / m 2 ;

[0013] or, the concentration of carnauba wax is 30-40%, and the coating amount is 5-10 g / m 2 ;

[0014] or, the concentration of polyurethane is 30-35%, and the coating amount is 2-5 g / m 2 ;

[0015] or, the concentration of waterborne acrylic resin is 60-70%, and the coating amount is 2-5 g / m 2 ;

[0016] or, the concentration of polyethylene wax is 10-15%, and the coating amount is 5-10 g / m 2 ;

[0017] or, the concentration of epoxidized soybean oil is 95-99%, and the coating amount is 5-10 g / m 2 ;

[0018] or, the concentration of liquid paraffin is 95-99%, and the coating amount is 3-8 g / m 2 ;

[0019] or, the concentration of chlorinated paraffin is 95-99%, and the coating amount is 3-8 g / m 2 ;

[0020] or, the concentration of epoxy resin is 70-80%, and the coating amount is 3-8 g / m 2 ;

[0021] or, the concentration of polymethylhydrogensiloxane is 95-99%, and the coating amount is 3-8 g / m 2 .

[0022] After high-viscosity beating, fines are more conducive to light transmission than coarser and longer fibers. When the beating degree of the pulp is 85-95°SR, the white ground film base paper already has a certain visible light transmission effect. After the functional layer is coated, the coating can fill the fiber voids, facilitating the passage of visible light and thus achieving the "transparent" effect. Although chlorinated paraffin, epoxy resin, liquid paraffin, polymethylhydrosiloxane, and epoxy soybean oil are all transparent hydrophobic coatings, it was found through experiments that when the ground film base paper is coated with epoxy soybean oil, its visible light transmittance is much higher than that of other transparent hydrophobic coatings.

[0023] The experiments compared bleached softwood pulp, bleached hardwood pulp, kenaf pulp, and waste corrugated paper pulp. (1) The base paper made from bleached softwood pulp is white, has weak light absorption, and is easy to coat with a functional coating subsequently to achieve transparency; (2) The formed paper exhibits the highest dry tensile strength and burst strength, etc., meeting the expected strength index requirements when laying (low basis weight, transparent ground film paper).

[0024] The step of first beating to a beating degree of 40-60°SR uses a Valley beater, which is suitable for low-viscosity beating of a large amount of pulp. After processing to a certain beating degree and obtaining pulp with a beating degree of 50°SR, a PFI refiner is then used for high-viscosity beating. The amount of pulp processed by this machine at one time is relatively small and it takes a long time. Therefore, beating in two stages can improve efficiency, save energy and time.

[0025] High-viscosity beating can fibrillate the coarse fibers in the original pulp into fine and short fibers, and the specific surface area of the fibers increases. After forming paper, the fibers inside the paper are closely packed with each other and the voids become smaller. When the beating degree is 85-95°SR, there is an obvious water vapor barrier effect compared with the unbeaten base paper. By surface coating with a transparent hydrophobic coating, a hydrophobic coating is formed on the paper surface to further block the permeation of water vapor. It was found through experiments that the moisture retention performance of the ground film base paper coated with an epoxy soybean oil coating is particularly good, and the water vapor transmission rate can reach 465 g / m 2 ·24h, far less than the specified 800 g / m 2 ·24h. By coating, a hydrophobic coating can be formed on the surface of the ground film base paper to achieve the purpose of soil and crop moisture conservation after laying. In addition, when the beating degree is 85-95°SR, the mechanical strength of the ground film base paper increases accordingly.

[0026] The biodegradable part of the white transparent ground film paper accounts for about 97% of the total mass, and it can be basically fully biodegradable after use.

[0027] The basis weight of the ground film base paper can be 30 g / m 2 This application does not make special limitations on the basis weight of the ground film base paper, which should be determined according to actual application requirements.

[0028] The inventors found through experiments that the addition of PVA can enhance the mechanical properties of the base paper.

[0029] Coat a non-transparent coating on one side of the original film paper, such as polyamide polyamine epichlorohydrin resin (PAE), carnauba wax, polyurethane, waterborne acrylic resin or polyethylene wax; coat a transparent coating on the other side, such as epoxidized soybean oil, liquid paraffin, chlorinated paraffin, epoxy resin or polymethylhydrosiloxane. However, the inventor found through experiments that when the transparent coating is coated alone, it is easy to have an adverse effect on the dry and wet strength of the film paper. The non-transparent coating refers to a coating that does not have an obvious transparent effect on the paper, and the coating itself can produce a good synergistic effect with the transparent coating after being coated, which can not only improve the water resistance, water vapor resistance, dry and wet strength of the film paper, but also help to further improve the transparency of the film paper.

[0030] The transparent coating has permeability and can penetrate into the fiber interior to improve the visible light transmittance of the original paper. Therefore, the two coatings are compound-coated to achieve the effects of transparency and simultaneously improving the water resistance, moisture resistance and strength of the film paper.

[0031] In some embodiments, polyurethane is coated on one side of the original film paper and epoxidized soybean oil is coated on the other side. After coating polyurethane alone, the water vapor transmission rate can reach 806 g / m 2 ·24h, and it has excellent wet tensile strength. When polyurethane and epoxidized soybean oil are combined, they can exhibit excellent wet tensile strength and a low water vapor transmission rate.

[0032] In some embodiments, PAE is coated on one side of the original film paper and epoxidized soybean oil is coated on the other side. Coating epoxidized soybean oil alone will slightly reduce the mechanical strength of the original paper, but after the combination of PAE and epoxidized soybean oil, it exhibits excellent dry tensile strength and simultaneously has other properties of the composite index.

[0033] In some embodiments, waterborne acrylic resin is coated on one side of the original film paper and liquid paraffin is coated on the other side. Coating waterborne acrylic resin or liquid paraffin alone can reduce the water vapor transmission to below 800 g / m 2 ·24h. After the combination of waterborne acrylic resin and liquid paraffin, it exhibits excellent dry tensile strength and excellent properties such as water vapor barrier.

[0034] In some embodiments, when the raw material is a mixed pulp of bleached softwood pulp and bleached hardwood pulp, the mass percentage of the bleached softwood pulp is greater than 60%.

[0035] The original film paper obtained by mixing a small amount of hardwood pulp (20-40%) into the softwood pulp for papermaking has similar physical properties compared with the 100% softwood pulp original film paper, but shows better surface smoothness than the pure softwood original paper. After adding, it is beneficial to reduce fiber flocculation and can reduce the coating amount of the coating. At the same time, it is beneficial to reduce production costs.

[0036] In some embodiments, when applying the functional coating, a 4-μm linear coating rod is used for single-sided or double-sided coating. Compared with the dipping method and the spraying method, the coating method can precisely control the amount of coating used, and the formed coating has good uniformity. The 4-μm linear coating rod can minimize the coating amount. The reference coating speed is 80 m / min.

[0037] In some embodiments, the dry strength agent is cationic polyacrylamide (CPAM) or cationic starch (CAS) or chitosan, and the addition amount of the dry strength agent is 1%-2.5% of the mass of the absolutely dry pulp. The dry strength agent can increase the dry tensile strength of the plastic film paper, and can increase the dry strength of the original plastic film paper by up to 27%.

[0038] In some embodiments, the wet strength agent is polyamide polyamine epichlorohydrin resin, and the addition amount of the wet strength agent is 1.5%-3% of the mass of the absolutely dry pulp, preferably 2.5%. The wet strength agent is used to increase the wet tensile strength of the plastic film paper, and can increase the wet strength of the original plastic film paper by up to 394%. When adding PAE wet strength agent, the plastic film paper has an obvious surface water resistance effect.

[0039] In some embodiments, the sizing agent is alkyl ketene dimer (AKD) or aluminum sulfate, and the addition amount of the sizing agent is 0.5%-2% of the mass of the absolutely dry pulp. After the sizing agent, the dry strength agent and the wet strength agent act together, they can increase the dry strength of the original plastic film paper by up to 30% and the wet strength by up to 444%.

[0040] In some embodiments, the retention aid is cationic / anionic polyacrylamide or cationic / anionic starch. The addition amount is 0.1-0.3% of the mass of the absolutely dry pulp. Excessive addition will cause the appearance of sediments.

[0041] In a second aspect, the present invention provides a white transparent plastic film paper prepared by the above preparation method.

[0042] The beneficial effects obtained by one or more of the above embodiments of the present invention are as follows:

[0043] 1) The water resistance Cobb of the plastic film paper 120 ≤20 g / m 2 , having certain hydrophobic properties, which is beneficial to extending the service life of the plastic film paper in a humid environment.

[0044] 2) The water vapor transmission rate ≤ 800 g / m 2 ·24 h, having a strong barrier property to water vapor, and can reduce soil moisture loss.

[0045] 3) Dry and wet tensile indices: the dry tensile index ≥ 40 N·m / g, and the wet tensile index ≥ 35% of the dry tensile index, ensuring that the plastic film paper does not break and fester during the covering period.

[0046] 4) The light transmittance ≥ 85%, enabling most of the visible light to pass through, achieving effects such as warming the covered soil.

[0047] 5) The relative biodegradation rate ≥ 90%. After use, it can be completely or mostly degraded into organic matter and enter the soil, which is beneficial to improving the soil structure. Description of the Drawings

[0048] The schematic diagram of the drawings forming part of the present invention is used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0049] Figure 1 It is a schematic diagram of the structure of the white transparent plastic film paper prepared in the embodiment of the present invention;

[0050] Figure 2 It is a physical diagram of the white plastic film base paper (b) and the white transparent plastic film paper (a) prepared in Example 3 of the present invention.

[0051] In the figure, 1 is the plastic film base paper; 2 is the first functional coating; 3 is the second functional coating. Detailed Embodiments

[0052] It should be noted that the following detailed descriptions are all illustrative and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0053] The present invention will be further described below in conjunction with embodiments.

[0054] Example 1

[0055] Papermaking of the plastic film base paper: Select about 500 g of bleached softwood pulp with absolute dry weight, and pass it through a Valley beater and a PFI refiner in sequence. The beating degrees of the final pulp are 80°SR, 85°SR, 90°SR, and 95°SR.

[0056] After the beating is completed, most of the water is filtered out with a pulp bag, and then it is placed in a 5°C low-temperature refrigerator for 24 h to balance the moisture, and the solid content is measured.

[0057] The solid content of the beaten pulp is measured by the five-point sampling method, including the following steps: Sampling is carried out on the pulp after moisture balance by the five-point sampling method, and the sample mass is recorded as m1. Then the sample is put into an oven at 105°C and taken out after 24 h, and the mass is measured and recorded as m2. The calculation formula A for the solid content is: A = (m2 ÷ m1) × 100%.

[0058] Take 0.94 g of absolute dry pulp, 2% CPAM dry strength agent, 2.5% PAE wet strength agent, 1% AKD sizing agent, and 0.1% retention aid based on the weight of the absolute dry pulp. Blend them in a refiner and refine at 10,000 revolutions to completely disperse the fibers. After refining, send the pulp to a paper machine to obtain a base paper for plastic film with a basis weight of 30 g / m 2 of the base paper for plastic film.

[0059] Coating experiment of the base paper for plastic film: Fix the white base paper for plastic film and scrape a layer of epoxidized soybean oil on one side of the white base paper with a 4-μm linear coating rod. The coating concentration is 99%, and dry it at 30 °C for 1 h.

[0060] The relevant properties of the obtained plastic film papers with different beating degrees are shown in Table 1.

[0061] Table 1 Properties of plastic film papers prepared with different beating degrees

[0062]

[0063] Example 2

[0064] Papermaking of the base paper for plastic film: Select about 500 g of bleached softwood pulp and bleached hardwood pulp with an absolute dry weight. Pass them through a Valley beater and a PFI mill in sequence. The beating degree of the final pulp is 90 °SR. After the beating is completed, filter out the vast majority of the moisture with a pulp bag, and then put it into a low-temperature refrigerator at 5 °C for 24 h to balance the moisture, and measure the solid content.

[0065] Weigh the two kinds of bleached pulp according to the proportion of bleached hardwood pulp being 10%, 20%, and 40%, as well as 2% CPAM dry strength agent, 2.5% PAE wet strength agent, 1% AKD sizing agent, and 0.1% retention aid based on the weight of the absolute dry pulp. Blend them in a refiner and refine at 10,000 revolutions to completely disperse the fibers. After refining, send the pulp to a paper machine to obtain a base paper for plastic film with a basis weight of 30 g / m 2 of the base paper for plastic film.

[0066] Coating experiment of the base paper for plastic film: Fix the white base paper for plastic film and scrape a layer of epoxidized soybean oil on one side of the white base paper with a 4-μm linear coating rod. The coating concentration is 99%, and dry it at 30 °C for 1 h.

[0067] The relevant properties of the obtained plastic film papers are shown in Table 2.

[0068] Table 2 Properties of plastic film papers with different dry strength agent addition amounts

[0069]

[0070] Example 3

[0071] Manufacture of base paper for plastic film: Select about 500 g of bleached softwood pulp with dry weight, pass it through a Valley beater and a PFI refiner in sequence, and the beating degree of the final pulp is 90°SR. After the beating is completed, filter out the vast majority of water with a pulp bag, then put it into a low-temperature refrigerator at 5°C for 24 h to balance the moisture, and measure the solid content.

[0072] Take 0.94 g of dry pulp, 2% CPAM dry strength agent, 2.5% PAE wet strength agent, 1% AKD sizing agent and 0.1% retention aid by weight of dry pulp, mix them in a disintegrator, and disintegrate at 10,000 revolutions to completely disperse the fibers. After disintegration, send the pulp to a paper machine to obtain a base paper for plastic film of 30 g / m 2 of the plastic film.

[0073] Coating experiment of base paper for plastic film: Fix the white base paper for plastic film, and scrape a layer of epoxidized soybean oil on one side of the white base paper with a 4-μm linear coating rod, the coating concentration is 99%, and dry at 30°C for 1 h.

[0074] The relevant properties of the obtained plastic film paper are shown in Table 3.

[0075] Table 3 Properties of plastic film paper

[0076]

[0077] Example 4

[0078] Manufacture of base paper for plastic film: Select about 500 g of bleached softwood pulp and bleached hardwood pulp with dry weight, pass it through a Valley beater and a PFI refiner in sequence, and the beating degree of the final pulp is 90°SR. After the beating is completed, filter out the vast majority of water with a pulp bag, then put it into a low-temperature refrigerator at 5°C for 24 h to balance the moisture, and measure the solid content.

[0079] Take 0.94 g of mixed dry pulp (20% of bleached hardwood dry pulp) and papermaking additives of 1%, 1.5%, 2%, 2.5% CPAM dry strength agent, 2.5% PAE wet strength agent, 1% AKD sizing agent and 0.1% retention aid by weight of dry pulp, mix them in a disintegrator, and disintegrate at 10,000 revolutions to completely disperse the fibers. After disintegration, send the pulp to a paper machine to obtain a base paper for plastic film of 30 g / m 2 of the plastic film.

[0080] Coating experiment of base paper for plastic film: Fix the white base paper for plastic film, and scrape a layer of epoxidized soybean oil on one side of the white base paper with a 4-μm linear coating rod, the coating concentration is 99%, and dry at 30°C for 1 h.

[0081] The relevant properties of the obtained plastic film paper with different dry strength agent addition amounts are shown in Table 4.

[0082] Table 4 Properties of plastic film paper with different dry strength agent addition amounts

[0083]

[0084] Example 5

[0085] Manufacture of the base paper for plastic film: Select about 500 g of bleached softwood pulp and bleached hardwood pulp with dry weight, pass through a Valley beater and a PFI refiner in sequence, and the beating degree of the final pulp is 90° SR. After the beating is completed, filter out the vast majority of water with a pulp bag, then put it into a low-temperature refrigerator at 5 °C for 24 h to balance the moisture, and measure the solid content.

[0086] Take 0.94 g of mixed dry pulp (20% of bleached hardwood dry pulp) and papermaking aids of 2% CPAM dry strength agent, 1.5%, 2%, 2.5%, 3% PAE wet strength agent, 1% AKD sizing agent and 0.1% retention aid based on the dry weight of the dry pulp, blend them in a disintegrator, and disintegrate at 10,000 rpm to completely disperse the fibers. After disintegration, send the pulp to a paper machine to obtain a base paper for plastic film of 30 g / m 2 of the base paper for plastic film.

[0087] Coating experiment of the base paper for plastic film: Fix the white base paper for plastic film, scrape a layer of epoxidized soybean oil with a concentration of 99% on the surface of the white base paper for plastic film with a 4-μm linear coating rod, and dry it at 30 °C for 1 h.

[0088] The relevant properties of the plastic film papers with different wet strength agent addition amounts prepared are shown in Table 5.

[0089] Table 5 Properties of Plastic Film Papers with Different Wet Strength Agent Addition Amounts

[0090]

[0091] Example 6

[0092] Manufacture of the base paper for plastic film: Select about 500 g of bleached softwood pulp and bleached hardwood pulp with dry weight, pass through a Valley beater and a PFI refiner in sequence, and the beating degree of the final pulp is 90° SR. After the beating is completed, filter out the vast majority of water with a pulp bag, then put it into a low-temperature refrigerator at 5 °C for 24 h to balance the moisture, and measure the solid content. Take 0.94 g, 1.26 g and 1.57 g of mixed dry pulp (20% of bleached hardwood dry pulp) and papermaking aids of 2% CPAM dry strength agent, 2.5% PAE wet strength agent, 1% AKD sizing agent and 0.1% retention aid based on the dry weight of the dry pulp, blend them in a disintegrator, and disintegrate at 10,000 rpm to completely disperse the fibers. After disintegration, send the pulp to a paper machine to obtain base papers for plastic film with basis weights of 30, 40 and 50 g / m 2 of the base paper for plastic film.

[0093] Coating experiment of the base paper for plastic film: Fix the white base paper for plastic film, and scrape a layer of epoxidized soybean oil on one side of the white base paper with a 4-μm linear coating rod, then dry it at 30 °C for 1 h.

[0094] The relevant properties of the plastic film papers made from different basis weight base papers for plastic film are shown in Table 6.

[0095] Table 6 Properties of plastic film papers with different basis weights

[0096]

[0097] Example 7

[0098] Papermaking of the base paper for plastic film: Select about 500 g of bleached softwood pulp and bleached hardwood pulp by oven dry weight, pass them through a Valley beater and a PFI refiner in sequence, and the beating degree of the final pulp is 90 °SR. After the beating is completed, filter out the vast majority of the moisture with a pulp bag, then put it into a low-temperature refrigerator at 5 °C for 24 h to balance the moisture, and measure the solid content.

[0099] Take 0.94 g of mixed pulp by oven dry weight (20% of bleached hardwood pulp by oven dry weight), as well as PVA accounting for 1%, 1.5%, and 2% of the pulp by oven dry weight, 2% of dry strength agent CPAM, 2.5% of wet strength agent PAE, 1% of sizing agent AKD, and 0.1% of retention aid as papermaking additives. Blend them in a disintegrator and disintegrate at 20,000 revolutions to completely disperse the fibers. After disintegration, send the pulp to a paper machine to obtain a base paper for plastic film with a basis weight of 30 g / m 2 of the base paper for plastic film.

[0100] Coating experiment of the base paper for plastic film: Fix the white base paper for plastic film, and scrape a layer of epoxidized soybean oil on one side of the white base paper with a 4-μm linear coating rod, then dry it at 30 °C for 1 h.

[0101] The relevant properties of the plastic film papers made from the base papers for plastic film with different PVA addition amounts are shown in Table 7.

[0102] Table 7 Properties of plastic film papers with different PVA addition amounts

[0103]

[0104] PVA is an environmentally friendly and green material. After adding it, the bonding strength between fibers can be enhanced, thereby improving the dry and wet tensile strengths. It can also improve the weather resistance of the paper and extend its service life.

[0105] Example 8

[0106] Manufacture of the base paper for plastic film: Select about 500 g of bleached softwood pulp and bleached hardwood pulp with absolute dry weight, pass through a Valley beater and a PFI refiner in sequence, and the beating degree of the final pulp is 90°SR. After beating, filter out the vast majority of water with a pulp bag, then put it into a low-temperature refrigerator at 5°C for 24 h to balance the moisture, and measure the solid content.

[0107] Take 0.94 g of mixed absolute dry pulp (20% of bleached hardwood absolute dry pulp) and papermaking aids including 1.5% PVA, 2% CPAM dry strength agent, 2.5% PAE wet strength agent, 1% AKD sizing agent and 0.1% retention aid based on the weight of the absolute dry pulp, blend them in a disintegrator, and disintegrate at 20,000 revolutions to completely disperse the fibers. After disintegration, send the pulp to a paper machine to obtain a base paper for plastic film with a basis weight of 30 g / m 2 of the plastic film.

[0108] Coating experiment of the base paper for plastic film: Fix the white base paper for plastic film, and scrape a layer of polyamide polyamine epichlorohydrin resin (PAE), carnauba wax, polyurethane, waterborne acrylic resin or polyethylene wax on one side of the white base paper with a 4-μm linear coating rod. Dry the polyurethane at 110°C and dry the other coatings at 30°C for 1 h.

[0109] After diluting PAE with water to a concentration of 1%, perform the coating.

[0110] Carnauba wax (30%), polyurethane (33%), and waterborne acrylic resin (70%) are purchased reagents, all in emulsion form and without dilution treatment. The concentrations during coating are 30%, 33%, and 70% respectively.

[0111] The polyethylene wax emulsion is a purchased reagent, which is diluted with water to a concentration of 10% before coating.

[0112] The concentration of PAE is about 1%. After single-sided coating with PAE, it shows excellent dry tensile strength. As a cationic additive, PAE itself has many positive charges, which can combine with the hydroxyl groups on the fibers to improve the dry strength. And it forms a hydrophobic layer on the paper surface, improving the wet strength to a certain extent.

[0113] Carnauba wax is a purchased reagent with a concentration of about 30%. After coating, the wet strength is significantly improved, but the dry strength and water vapor barrier are poor.

[0114] The concentration of polyurethane is about 33%. After coating, the wet strength is improved most significantly.

[0115] Waterborne acrylic resin is a purchased reagent with a concentration of about 70%. After coating, the hydrophobic property and water vapor barrier property are obvious.

[0116] After diluting polyethylene wax to 10%, perform the coating. After coating, it has good hydrophobic and moisture barrier properties, but the improvement of mechanical properties is not obvious.

[0117] After the above coating, the transparency effect is related to the coating amount and does not significantly improve the transparency of the base paper, which is about between 70% and 80%.

[0118] The relevant properties of the mulch paper made from different hydrophobic and moisture-proof non-transparent coating base papers are shown in Table 8.

[0119] Table 8 Properties of Mulch Papers with Different Hydrophobic Coatings

[0120]

[0121]

[0122] Example 9

[0123] Papermaking of the mulch paper base: Select about 500 g of absolutely dry weight of bleached softwood pulp and bleached hardwood pulp, pass through a Valley beater and a PFI refiner in sequence, and the beating degree of the final pulp is 90° SR. After the beating is completed, filter out the vast majority of the moisture with a pulp bag, then put it into a low-temperature refrigerator at 5 °C for 24 h to balance the moisture, and measure the solid content.

[0124] Take 0.94 g of mixed absolutely dry pulp (20% of bleached hardwood absolutely dry pulp) and papermaking additives of 1.5% PVA, 2% CPAM dry strength agent, 2.5% PAE wet strength agent, 1% AKD sizing agent and 0.1% retention aid, blend them in a dissolver, and defibrate at 10,000 revolutions to completely disperse the fibers. After defibration, send the pulp to a paper machine to obtain a mulch paper base of 30 g / m 2 of the mulch paper base.

[0125] Coating experiment of the mulch paper base: Fix the white mulch paper base, and scrape a layer of any one of the coatings of epoxy resin, chlorinated paraffin, liquid paraffin, polymethylhydrogensiloxane, and epoxy soybean oil on one side of the white mulch paper base with a 4-μm linear coating rod, and dry it at 30 °C for 1 h.

[0126] The actual concentration of epoxy soybean oil is 99%; the actual concentration of liquid paraffin is 99%; the actual concentration of chlorinated paraffin is 99%; the actual concentration of epoxy resin is 70%; the actual concentration of polymethylhydrogensiloxane is 99%.

[0127] The relevant properties of the mulch papers made from different hydrophobic coatings are shown in Table 9.

[0128] Table 9 Properties of Mulch Papers Made from Different Hydrophobic Coating Bases

[0129]

[0130] The performance analysis of the mulch paper coated with epoxy soybean oil is as follows:

[0131] The water resistance Cobb of the plastic film paper 120 is 10.2 g / m 2 , showing excellent hydrophobic performance, which is beneficial to the sliding of water droplets on the surface of the plastic film paper and prolongs the service life of the plastic film paper.

[0132] The water vapor transmission rate is 477 g / m 2 ·24 h. Through the coating process, good water vapor barrier performance is given to the plastic film paper, which can effectively prevent the loss of moisture in the soil and crops, and achieve the effect of increasing production and efficiency.

[0133] Dry and wet tensile indices: The dry tensile index is 50.2 N·m / g, and the wet tensile index is 20.1 N·m / g. The higher dry strength enables the plastic film paper to meet the agronomic requirements of film mulching, and the wet tensile index reaches 37% of the dry tensile index, ensuring that it is not easily damaged and festered during the covering period. After the covering period ends, as the strength of the plastic film paper gradually decreases, it can be degraded into organic matter and enter the soil, which is beneficial to improving the soil structure.

[0134] The light transmittance is 89%, ensuring that sufficient visible light can penetrate the plastic film to meet the lighting conditions required by crops, and playing the role of replacing transparent plastic film.

[0135] Example 10

[0136] Manufacture of the base paper of the plastic film: Select about 500 g of bleached softwood pulp and bleached hardwood pulp with absolute dry weight, and pass through a Valley beater and a PFI refiner in turn. The beating degree of the final pulp is 90° SR. After the beating is completed, most of the water is filtered out with a pulp bag, and then it is placed in a low-temperature refrigerator at 5°C for 24 h to balance the moisture, and the solid content is measured.

[0137] Take 0.94 g of mixed absolute dry pulp (20% of bleached hardwood absolute dry pulp) and papermaking additives of 1.5% PVA, 2% CPAM dry strength agent, 2.5% PAE wet strength agent, 1% AKD sizing agent and 0.1% retention aid based on the weight percentage of the absolute dry pulp, blend them in a disintegrator, and disintegrate at 20,000 revolutions to completely disperse the fibers. After disintegration, the pulp is sent to a paper machine to obtain the base paper of the plastic film with a basis weight of 30 g / m 2 of the plastic film.

[0138] Coating experiment of the base paper of the plastic film: Fix the white base paper of the plastic film, and scrape epoxy soybean oil (A), polyethylene wax and epoxy soybean oil (B), carnauba wax and epoxy soybean oil (C) on the front and back surfaces of the white base paper of the plastic film with a 4-μm linear coating rod respectively.

[0139] The polyethylene wax emulsion is a purchased reagent, which is diluted with water to a concentration of 10% before coating. The other coatings are not diluted. The actual concentration of epoxy soybean oil is 99%; the actual concentration of carnauba wax is 30%.

[0140] The relevant properties of the plastic mulch papers with different hydrophobic coatings are shown in Table 10.

[0141] Table 10 Properties of Plastic Mulch Papers with Different Hydrophobic Coatings

[0142]

[0143] Example 11

[0144] Papermaking of the plastic mulch base paper: Select about 500 g of bleached softwood pulp and bleached hardwood pulp by dry weight, pass them through a Valley beater and a PFI refiner in sequence, and the beating degree of the final pulp is 90° SR. After the beating is completed, filter out the vast majority of the moisture with a pulp bag, then put it into a low-temperature refrigerator at 5 °C for 24 h to balance the moisture, and measure the solid content.

[0145] Take 0.94 g of mixed dry pulp (20% of bleached hardwood dry pulp) and papermaking additives of 1.5% PVA, 2% CPAM dry strength agent, 2.5% PAE wet strength agent, 1% AKD sizing agent and 0.1% retention aid by dry pulp weight, blend them in a disintegrator, and disintegrate at 20,000 revolutions to completely disperse the fibers. After disintegration, send the pulp to a paper machine to obtain a plastic mulch base paper with a basis weight of 30 g / m 2 of the plastic mulch base paper.

[0146] Coating experiment of the plastic mulch base paper: Fix the white plastic mulch base paper, and scrape polyurethane and epoxidized soybean oil (D), polyamide polyamine epichlorohydrin resin and epoxidized soybean oil (E), or waterborne acrylic resin and liquid paraffin (F) on the front and back surfaces of the white plastic mulch base paper respectively with a 4-μm linear coating rod.

[0147] Dilute polyamide polyamine epichlorohydrin resin (PAE) to 1% before coating. Other coatings are not diluted. The actual concentration of polyurethane is 33%. The actual concentration of epoxidized soybean oil is 99%. The actual concentration of waterborne acrylic resin is 70%.

[0148] The relevant properties of the plastic mulch papers with different hydrophobic coatings are shown in Table 11.

[0149] Table 11 Properties of Plastic Mulch Papers of Plastic Mulch Base Papers with Different Hydrophobic Coatings

[0150]

[0151] The combination of polyurethane and epoxidized soybean oil shows the most obvious improvement in the wet tensile index of the base paper. The combination of polyamide polyamine epichlorohydrin resin and epoxidized soybean oil shows the most obvious improvement in the dry tensile index of the base paper. The combination of waterborne acrylic resin and liquid paraffin shows the most obvious improvement in the hydrophobicity (Cobb120) and water vapor barrier performance of the base paper.

[0152] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a white transparent plastic mulch paper, characterized in that: The method includes the following steps: Beating bleached softwood pulp or a mixed pulp of bleached softwood pulp and bleached hardwood pulp to a beating degree of 40 - 60°SR first, and then performing multiple grindings to obtain a pulp with a beating degree of 85 - 95°SR; Then adding PVA and papermaking aids to the pulp, fully mixing, defibrating, and then papermaking to obtain the base paper for plastic film; the papermaking aids include dry strength agent, wet strength agent, sizing agent, and retention aid; the PVA is added in the form of an aqueous solution, and the solid content of PVA is 1% - 2% based on the mass percentage of the absolutely dry pulp; Coating one side of the base paper for plastic film with polyurethane and the other side with epoxy soybean oil; Or, coating one side of the base paper for plastic film with PAE and the other side with epoxy soybean oil; Or, coating one side of the base paper for plastic film with waterborne acrylic resin and the other side with liquid paraffin, and drying to obtain the product.

2. The preparation method of the white transparent plastic mulch paper according to claim 1, wherein: PAE concentration is 1 - 5%, coating amount is 5 - 10 g / m 2 ; Or, the polyurethane concentration is 30 - 35%, and the coating amount is 2 - 5 g / m 2 ; Or, the concentration of the water-based acrylic resin is 60-70%, and the coating amount is 2-5 g / m 2 ; Or, the concentration of epoxidized soybean oil is 95 - 99%, and the coating amount is 5 - 10 g / m 2 ; Or, the concentration of liquid paraffin is 95 - 99%, and the coating amount is 3 - 8 g / m 2 .

3. The preparation method of the white transparent plastic mulch paper according to claim 1, characterized in that: When the raw material is a mixed pulp of bleached softwood pulp and bleached hardwood pulp, the mass percentage of the bleached softwood pulp is greater than 60%.

4. The preparation method of the white transparent plastic mulch paper according to claim 1, wherein: When coating the functional coating, a 4μm linear coating rod is used for single-sided or double-sided coating.

5. The preparation method of the white transparent plastic mulch paper according to claim 1, characterized in that: The dry strength agent is cationic polyacrylamide or cationic starch or chitosan, and the addition amount of the dry strength agent is 1% - 2.5% of the mass of the absolutely dry pulp.

6. The preparation method of the white transparent plastic film paper according to claim 1, characterized in that: The wet strength agent is polyamide polyamine epichlorohydrin resin, and the addition amount of the wet strength agent is 1.5% - 3% of the mass of the absolutely dry pulp.

7. The preparation method of the white transparent plastic mulch paper according to claim 1, characterized in that: The sizing agent is alkyl ketene dimer or aluminum sulfate, and the addition amount of the sizing agent is 0.5% - 2% of the mass of the absolutely dry pulp.

8. The preparation method of the white transparent plastic mulch paper according to claim 1, characterized in that: The retention aid is cationic / anionic polyacrylamide or cationic / anionic starch.

9. A white transparent plastic mulch paper, characterized in that: Prepared by the preparation method according to any one of claims 1 - 8.

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