A plastic film paper for greenhouse and its preparation method

Abstract

The present invention belongs to the technical field of plastic film paper, and discloses a plastic film paper for greenhouses and a preparation method thereof, which comprises the following steps: beating wheat straw bio-mechanical pulp, with the beating degree being 35-40°SR, to obtain a slurry; fully mixing the slurry with a papermaking aid and then sheet-forming to obtain a base paper for the plastic film; uniformly coating the one side or both sides of the base paper for the plastic film with gelatinized cationic starch or gelatinized soybean oil-modified starch, and drying; then uniformly coating a polyurethane or acrylic resin coating on the one side or both sides, and drying to obtain the product. This plastic film uses bio-mechanical pulp as the main raw material, and through the methods of internal sizing addition and surface coating, realizes high physical and mechanical properties and high hydrophobic and moisture-barrier properties of the plastic film paper, can replace black plastic mulch films, and solve problems such as environmental pollution caused by plastic mulch films.

Description

Technical Field

[0001] The present invention belongs to the technical field of plastic mulch paper, and particularly relates to a plastic mulch paper for greenhouses 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] As a large agricultural country, China has become the world's largest producer and user of agricultural films. At present, most of the plastic mulches are mainly made of petroleum-based plastics such as polyvinyl chloride (PVC) and polyethylene (PE), which are difficult to be completely degraded when remaining in the soil and damage the ecology. Black plastic mulch is a kind of plastic mulch often laid in crop greenhouses, which can play the roles of heat preservation, moisture preservation, weed control, etc. It is often used to improve the growth environment of crops, increase the fertilizer utilization rate, and avoid the influence of weeds on the quality of crops.

[0004] Due to environmental pollution problems caused by plastic mulches, degradable mulches have gradually become the focus of research, among which paper-based mulches have certain advantages. Paper-based mulches are made from plant fibers, mixed according to different slurries or different ratios, and obtained through papermaking preparation technology. They have certain dry strength and light-shielding properties. However, the light-shielding property of paper-based mulches is not as good as that of black plastic mulches, so their performance in inhibiting weed growth is not as good as that of black plastic mulches.

[0005] More importantly, traditional plastic-based black plastic mulches have good moisture preservation performance and can effectively prevent the evaporation of soil moisture. However, the water vapor barrier performance of paper-based mulches is poor and it is difficult to meet the moisture preservation performance requirements of black plastic mulches. In addition, the current paper-based mulches still do not have the high dry strength and high wet strength required for use in greenhouses. Moreover, the current preparation cost of paper-based mulches is relatively high, which has caused a great obstacle to their popularization and application.

[0006] Therefore, although the current paper-based mulches have good biodegradability, it is still very difficult to replace black plastic mulches. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a plastic mulch paper for greenhouses and a preparation method thereof. The plastic mulch uses biological mechanical pulp as the main raw material, and through the methods of in-pulp addition and surface coating, realizes the high physical and mechanical properties and high hydrophobic and moisture-barrier properties of the plastic mulch paper, can replace black plastic mulches, and solve environmental pollution problems caused by plastic mulches.

[0008] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a plastic film paper for a greenhouse, comprising the following steps: defibrating wheat straw biopulping and then performing beating treatment with a beating degree of 35-40°SR to obtain a slurry;

[0010] After fully mixing the slurry with a papermaking aid, sheet forming is carried out to obtain a base paper for the plastic film;

[0011] Uniformly coat the one side or both sides of the base paper for the plastic film with gelatinized cationic starch or gelatinized soybean oil-modified starch, and dry; when gelatinizing, the mass percentage of the cationic starch aqueous solution is 3-10%; the mass percentage of starch in the soybean oil-modified starch is 2.5-10%;

[0012] Then uniformly coat a polyurethane or acrylic resin coating on the one side or both sides, and obtain the product after drying.

[0013] In some embodiments, the papermaking aid includes cationic polyacrylamide (CPAM) or cationic starch (CAS) or chitosan accounting for 0.5%-3% of the absolute dry pulp mass, polyamide polyamine epichlorohydrin accounting for 1.5%-3% of the absolute dry pulp mass, alkyl ketene dimer (AKD) or aluminum sulfate accounting for 0.5%-2% of the absolute dry pulp mass, and cationic / anionic polyacrylamide or cationic / anionic starch accounting for 0.1%-0.3% of the absolute dry pulp mass.

[0014] The biopulping is first prepared by biological enzyme pretreatment and then by mechanical pulping. The biological enzyme is a complex enzyme composed of pectinase, lipase and xylanase in a certain ratio. Using biopulping, it turns from traditional high-temperature and high-alkali pulping to low-temperature and less-alkali or alkali-free biological green pulping technology, combining modern biotechnology with agricultural straw mechanical pulping, and using biological enzyme preparations instead of traditional chemicals, which can not only solve the shortage of papermaking raw materials caused by the sharp reduction in waste paper imports, but also achieve zero discharge of wastewater.

[0015] By adding polyamide polyamine epichlorohydrin (PAE) wet strength agent in the pulp, the paper has obvious wet strengthening effect and surface water resistance, and the specific dosage is discussed. When the addition amount reaches 2.5%, the optimal effect is achieved (see Example 4 for details).

[0016] In order to achieve a water vapor transmission rate lower than 800 g / m 2 ·24h, the inventors discussed the in-pulp sizing process and the surface coating process. The first layer of the surface coating process is a gelatinized cationic starch layer or a modified starch coating. Just the gelatinized cationic starch layer or the modified starch layer can reduce the water vapor transmission rate from 2895 g / m 2 ·24h of the base paper to 2100 g / m 2· Less than 24h; The second layer is a hydrophobic moisture barrier coating, which is a coating of polyurethane or acrylic resin. Under the premise of reducing the coating amount as much as possible, the preferred two hydrophobic moisture barrier coatings both make the water vapor permeability of the ground film paper reach 800g / m 2 Less than 24 hours.

[0017] The hydrophobic moisture barrier coating can also enhance the mechanical properties and hydrophobic properties of the paper-based membrane.

[0018] The degradable part of the two natural-color mulch papers coated with acrylic resin and polyurethane accounted for more than 95% of the total mass, and they can basically achieve full biodegradation after use. Degradation experiments showed that the two mulch papers still maintained their original appearance after 80 days in the soil.

[0019] In order to reduce the visible light transmittance and achieve a visible light transmittance effect of less than 5%, wheat straw biomechanical pulp is used as the raw material, which has the advantages of environmental protection, low cost and opacity. The obtained mulch base paper has a low visible light transmittance of 3.6%. The subsequent gelatinized cationic starch or modified starch coating further reduces the transmittance, so that the mulch paper always maintains a visible light transmittance below 5%.

[0020] Through experiments, it is found that the gelatinized cationic starch layer or modified starch layer coated in the present invention can not only improve the water vapor barrier performance and visible light barrier performance of the paper-based film, but also improve the mechanical strength and smoothness of the paper-based film and reduce its water absorption rate. In addition, the gelatinized cationic starch layer or modified starch layer also has a good pore filling effect, which can reduce the amount of coating used in hydrophobic moisture barrier coatings such as polyurethane and acrylic resin, effectively save the preparation cost of ground film paper, and facilitate the promotion and application of ground film paper.

[0021] When 0.5-3% of the dry strength agent (cationic polyacrylamide (CPAM) or cationic starch (CAS) or chitosan) is added to the biomechanical pulp based on the absolute dry pulp mass, the dry strength of the base paper can be increased by up to about 30%.

[0022] When 1.5-3% of the mass of the absolute dry pulp of a wet strength agent (polyamide polyamine epichlorohydrin) is added to the biomechanical pulp, the wet strength of the base paper can be increased by up to about 369%.

[0023] When 0.5-2% of the absolute dry pulp mass of sizing agent (alkyl ketene dimer (AKD) or aluminum sulfate) is added to the biomechanical pulp, the sizing agent works together with the dry strength agent and wet strength agent to increase the dry strength of the base paper by up to about 46% and its wet strength by about 400%.

[0024] When a retention aid (cationic / anionic polyacrylamide or cationic / anionic starch) of 0.1-0.3% of the oven-dry pulp mass is added to the biochemimechanical pulp, the retention rate during the pulp web formation can be effectively increased, and it has a good retention effect on fines, resulting in obvious pulp savings. Moreover, due to the good retention rate of fines, the light transmittance of the prepared paper-based film can be effectively reduced to better inhibit weed growth. When the addition amount of the retention aid is excessive, deposits will occur.

[0025] In some embodiments, it further includes the step of adding 0-40% by mass of waste corrugated paper pulp or 0-40% of wheat straw pulp to the wheat straw biochemimechanical pulp.

[0026] Adding waste corrugated paper pulp or wheat straw pulp to the wheat straw biochemimechanical pulp can reduce costs. Through experiments, it is found that when 0-40% by mass of waste corrugated paper pulp or wheat straw pulp is added to the wheat straw biochemimechanical pulp, the dry and wet strengths of the prepared paper-based film will not decrease significantly, and the dark waste corrugated paper pulp is more conducive to reducing the visible light transmittance of the film paper.

[0027] In some embodiments, the papermaking aids include cationic polyacrylamide or cationic starch or chitosan of 0.5%-2% of the oven-dry pulp mass, polyamide polyamine epichlorohydrin of 2%-3% of the oven-dry pulp mass, alkyl ketene dimer or aluminum sulfate of 0.5%-1% of the oven-dry pulp mass, and cationic / anionic polyacrylamide or cationic / anionic starch of 0.1%-0.2% of the oven-dry pulp mass.

[0028] Preferably, the papermaking aids include cationic polyacrylamide of 1%-2% of the oven-dry pulp mass, polyamide polyamine epichlorohydrin of 2%-3% of the oven-dry pulp mass, and alkyl ketene dimer of 0.5%-1% of the oven-dry pulp mass.

[0029] In some embodiments, the preparation method of the gelatinized cationic starch is: after adjusting the cationic starch aqueous solution to alkaline, heating it to 40-50°C and stirring for 20-40 min to obtain it.

[0030] Preferably, the mass percentage of the cationic starch aqueous solution is 3-10%, preferably 7%.

[0031] Preferably, in the cationic starch aqueous solution, the mass percentage of sodium hydroxide is 8%-15%.

[0032] In some embodiments, the preparation method of the gelatinized soybean oil-modified starch is: adding soybean oil and sodium carbonate to the dimethyl sulfoxide solution of starch to obtain a mixed solution, heating it to 110-150°C, and the heating time is 1-3 h to hydrophobically modify the starch to obtain the modified starch.

[0033] Soybean oil replaces hydroxyl groups to esterify and modify starch, which can effectively improve the hydrophobic property of starch. Sodium carbonate is used as a catalyst to promote the modification reaction.

[0034] Preferably, in the mixed solution, the mass percentage of starch is 2.5 - 10%; the mass percentage of soybean oil is 8 - 12%; the mass percentage of sodium carbonate is 13 - 17%.

[0035] Preferably, the modified starch undergoes the same gelatinization process as cationic starch.

[0036] In some embodiments, the coating method of gelatinized cationic starch or gelatinized soybean oil - modified starch is as follows: using a 10 - μm linear coating rod to coat on the surface of the original film paper, and then drying it.

[0037] Preferably, the single - side coating amount of gelatinized cationic starch or gelatinized soybean oil - modified starch is 1.5 - 2 g / m 2 , and the double - side coating amount is 3 - 4 g / m 2 .

[0038] In some embodiments, the coating method of the hydrophobic and moisture - resistant coating is as follows: using a 4 - μm linear coating rod to coat on the surface of the gelatinized cationic starch or gelatinized modified starch coating, and then drying it to obtain the product.

[0039] Preferably, the single - side coating amount of polyurethane is 1.5 - 2 g / m 2 , and the double - side coating amount is 3 - 4 g / m 2 .

[0040] Preferably, the single - side coating amount of acrylic resin is 2.5 - 3 g / m 2 , and the double - side coating amount is 5 - 6 g / m 2 .

[0041] Compared with the dipping method and the spraying method, the coating method can accurately control the amount of coating used, and the formed coating has good uniformity. The 4 - μm linear coating rod can minimize the coating amount.

[0042] In some embodiments, the basis weight of the original film paper is 60 - 70 g / m 2 .

[0043] The drying temperatures of both the polyurethane and acrylic resin coatings are 105 - 110 °C.

[0044] In the second aspect, the present invention provides a greenhouse film paper prepared by the above - mentioned preparation method.

[0045] The beneficial effects obtained by one or more of the above - mentioned embodiments of the present invention are as follows:

[0046] 1) The water resistance Cobb of the 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.

[0047] 2) Water vapor transmission rate ≤ 800 g / m 2 ·24 h, having strong barrier properties to water vapor, which can reduce soil water loss.

[0048] 3) Physical strength index: Tear index ≥ 2.5 mN·m 2 / g, burst resistance index ≥ 2 kPa·m 2 / g, wet tensile index ≥ 25% of the dry tensile index, so that the plastic film paper does not break and fester during the covering period.

[0049] 4) Light transmittance ≤ 5%, which can effectively inhibit the growth and development of weeds and achieve the purpose of inhibiting weed growth.

[0050] 5) 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The specification drawings forming a part of the present invention are 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 of the present invention.

[0052] Figure 1 It is a preparation flow chart of the natural color degradable plastic film paper for greenhouse. DETAILED DESCRIPTION OF THE INVENTION

[0053] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0054] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations rather than limitations of the present invention.

[0055] Example 1

[0056] Papermaking of the base paper of the plastic film: Take about 500 g of absolutely dry weight of bio-mechanical pulp and beat it with a Valley beater to obtain bio-mechanical pulp with beating degrees of about 20°SR, 30°SR, and 40°SR respectively. After the beating is completed, filter out the vast majority of water with a pulp bag, put it into a 5°C low-temperature refrigerator for 24 h to balance the moisture, and measure the solid content.

[0057] Take 1.88 g of absolute dry pulp and papermaking additives including 0.5% CPAM dry strength agent, 2% PAE wet strength agent, 0.5% AKD sizing agent and 0.1% retention aid based on the weight of the absolute dry pulp. Blend them in a refiner and defibrate at 10,000 revolutions to completely disperse the fibers. After defibration, send the pulp to a paper machine to obtain a base paper for plastic film with a basis weight of 60 g / m 2 of the base paper for plastic film.

[0058] Coating experiment of the base paper for plastic film: First, prepare an aqueous solution of 5 wt% cationic starch, and then add 10% sodium hydroxide based on the mass of the starch. Stir mechanically at 40 °C for 30 min at 10,000 revolutions to obtain gelatinized cationic starch. Fix the base paper for plastic film and evenly coat the front side of the base paper for plastic film with the gelatinized cationic starch using a 10-μm wire-wound rod, and dry at 80 °C for 10 min. Take it out and continue to coat polyurethane on the starch layer on the front side using a 4-μm wire-wound rod, and dry at 110 °C for 10 min to obtain the product.

[0059] The properties of the plastic film papers prepared with different beating degrees are shown in Table 1.

[0060] Table 1 Properties of the plastic film papers prepared with different beating degrees

[0061]

[0062]

[0063] Example 2

[0064] Papermaking of the base paper for plastic film: Take about 500 g of bio-mechanical pulp with an absolute dry weight, beat it with a Valley beater to obtain bio-mechanical pulp with a beating degree of about 40 °SR. After the beating is completed, filter out the vast majority of the moisture with a pulp bag, put it into a low-temperature refrigerator at 5 °C for 24 h to balance the moisture, and measure the solid content.

[0065] Take 1.88 g and 2.19 g of absolute dry pulp and papermaking additives including 0.5% CPAM dry strength agent, 2% PAE wet strength agent, 0.5% AKD sizing agent and 0.1% retention aid based on the weight of the absolute dry pulp. Blend them in a refiner and defibrate at 10,000 revolutions to completely disperse the fibers. After defibration, send the pulp to a paper machine to obtain base papers for plastic film with basis weights of 60 g / m 2 and 70 g / m 2 of the base paper for plastic film.

[0066] Coating experiment of the base paper for plastic film: First, prepare an aqueous solution of 5 wt% cationic starch, and then add 10% sodium hydroxide based on the mass of the starch. Stir mechanically at 40 °C for 30 min at 10,000 revolutions to obtain gelatinized cationic starch.

[0067] Fix the base paper for plastic film, and evenly coat the front side of the base paper for plastic film with gelatinized cationic starch using a 10-μm linear coating rod, then dry it at 80 °C for 10 min. Take it out, and continue to coat the starch layer on the front side with polyurethane using a 4-μm linear coating rod, and dry it at 110 °C for 10 min to obtain the product.

[0068] The properties of the prepared plastic film papers with different basis weights are shown in Table 2.

[0069] Table 2 Properties of Plastic Film Papers Prepared with Different Papermaking Basis Weights

[0070]

[0071] Example 3

[0072] Papermaking of the base paper for plastic film: Take about 500 g of absolutely dry weight of bio-mechanical pulp, beat it with a Valley beater for about 20 min, the beating degree is about 40 °SR. After the beating is completed, filter out the vast majority of water with a pulp bag, put it into a 5 °C low-temperature refrigerator for 24 h to balance the moisture, and measure the solid content.

[0073] Take 1.88 g of absolutely dry pulp, as well as papermaking aids including 0.5%, 1%, 1.5%, 2% CPAM dry strength agent by weight of the absolutely dry pulp, 2.5% PAE wet strength agent, 0.5% AKD sizing agent, and 0.1% retention aid, 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 the base paper for plastic film with a basis weight of 60 g / m 2 of the plastic film.

[0074] Coating experiment on the base paper for plastic film: First, prepare a 5% aqueous solution of cationic starch, and then add 10% sodium hydroxide by mass of the starch. At 40 °C, stir mechanically at 10,000 rpm for 30 min to obtain the gelatinized cationic starch.

[0075] Fix the base paper for plastic film, and evenly coat the front and back sides of the base paper for plastic film with gelatinized cationic starch using a 10-μm linear coating rod, then dry it at 80 °C for 10 min. Take it out, and continue to coat the starch layer on the front and back sides with polyurethane using a 4-μm linear coating rod, and dry it at 110 °C for 10 min to obtain the product.

[0076] The properties of the plastic film papers prepared with different contents of dry strength agent are shown in Table 3.

[0077] Table 3 Properties of Plastic Film Papers Prepared with Different Contents of Dry Strength Agent

[0078]

[0079] Example 4

[0080] Manufacture of the base paper for plastic film: Take about 500 g of bio-mechanical pulp with absolute dry weight, beat it with a Valle beating machine for about 20 min, with the beating degree about 40°SR. After the beating, filter out the vast majority of the moisture with a pulp bag, put it into a low-temperature refrigerator at 5°C for 24 h to balance the moisture, and measure the solid content.

[0081] Take 1.88 g of absolute dry pulp and papermaking aids including 1% CPAM dry strength agent, 2%, 2.5%, 3% PAE wet strength agent, 0.5% 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 10,000 revolutions to completely disperse the fibers. After disintegration, send the pulp to a paper machine to obtain the base paper for plastic film with a basis weight of 60 g / m 2 of the plastic film.

[0082] Coating experiment of the base paper for plastic film: First, prepare an aqueous solution of cationic starch with a concentration of 5 wt%, and then add sodium hydroxide accounting for 10% of the starch mass. Stir mechanically at 40°C for 30 min at 10,000 revolutions to obtain the gelatinized cationic starch.

[0083] Fix the base paper for plastic film, and evenly coat the gelatinized cationic starch on both the front and back sides of the base paper for plastic film with a 10-μm linear coating rod, and dry it at 80°C for 10 min. Take it out, and continue to coat polyurethane on the starch layers on both the front and back sides with a 4-μm linear coating rod, and dry it at 110°C for 10 min to obtain the product.

[0084] The properties of the plastic film papers prepared with different contents of wet strength agent are shown in Table 4.

[0085] Table 4 Properties of the plastic film papers prepared with different contents of wet strength agent

[0086]

[0087] Example 5

[0088] Manufacture of the base paper for plastic film: Take about 500 g of bio-mechanical pulp with absolute dry weight, beat it with a Valle beating machine for about 20 min, with the beating degree about 40°SR. After the beating, filter out the vast majority of the moisture with a pulp bag, put it into a low-temperature refrigerator at 5°C for 24 h to balance the moisture, and measure the solid content.

[0089] Mix 1.88 g of absolute dry pulp and papermaking aids including 1% CPAM dry strength agent, 2.5% PAE wet strength agent, 0.5% AKD sizing agent and 0.1% retention aid based on the weight of the absolute dry pulp 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 the base paper for plastic film with a basis weight of 60 g / m 2 of the plastic film.

[0090] Coating experiment of the base paper for plastic film: First, prepare 1%, 5%, and 7% aqueous solutions of cationic starch, and then add sodium hydroxide accounting for 10% of the starch mass. Stir mechanically at 10,000 revolutions per minute for 30 minutes at 40 °C to obtain gelatinized cationic starch.

[0091] Fix the base paper for plastic film, and evenly coat the gelatinized cationic starch on the front side of the base paper for plastic film with a 10-μm linear coating rod, and dry it at 80 °C for 10 minutes. Take it out, and continue to coat the acrylic resin on the starch layer on the front side with a 4-μm linear coating rod, and dry it at 110 °C for 10 minutes to obtain the product.

[0092] The properties of the plastic film papers prepared with different concentrations of cationic starch are shown in Table 5.

[0093] Table 5 Properties of the plastic film papers prepared with different concentrations of cationic starch

[0094]

[0095] As can be seen from Table 4, different concentrations of gelatinized cationic starch result in different actual coating amounts of starch; when the concentration of gelatinized cation increases, its pore filling effect on fibers improves, resulting in a decrease in the coating amount of acrylic resin, and the relevant properties of the plastic film paper can also meet the requirements.

[0096] Example 6

[0097] Papermaking of the base paper for plastic film: Take about 500 g of bio-mechanical pulp with an absolute dry weight, beat it with a Valley beater for about 20 minutes, with a beating degree of about 40 °SR. After the beating is completed, filter out the vast majority of the water with a pulp bag, put it into a low-temperature refrigerator at 5 °C for 24 hours to balance the moisture, and measure the solid content.

[0098] Mix 1.88 g of absolute dry pulp and papermaking additives including 1% CPAM dry strength agent, 2.5% PAE wet strength agent, 0.5% AKD sizing agent, and 0.1% retention aid based on the weight percentage of the absolute dry pulp in a dissolver, and disperse at 10,000 revolutions per minute to completely disperse the fibers. After dispersion, send the pulp to a paper machine to obtain a base paper for plastic film with a basis weight of 60 g / m 2 of the base paper for plastic film.

[0099] Coating experiment of the base paper for plastic film: First, prepare a 7% aqueous solution of cationic starch, and then add sodium hydroxide accounting for 10% of the starch mass. Stir mechanically at 10,000 revolutions per minute for 30 minutes at 40 °C to obtain gelatinized cationic starch. Fix the base paper for plastic film, and evenly coat the gelatinized cationic starch on both the front and back sides of the base paper for plastic film with a 10-μm linear coating rod, and dry it at 80 °C for 10 minutes. Take it out, and continue to coat polycaprolactone (PCL), polyvinylidene chloride (PVDC), and modified starch on the starch layers on both the front and back sides with a 4-μm linear coating rod, and dry it at 30 °C for 10 minutes to obtain the product.

[0100] The properties of the plastic film papers prepared with different hydrophobic and moisture barrier coatings are shown in Table 6.

[0101] Table 6 Properties of the plastic film papers prepared with different hydrophobic and moisture barrier coatings

[0102]

[0103]

[0104] During the experiment, the coating effects of PCL and PVDC were compared. Although they have excellent hydrophobic and water vapor barrier properties, the coating process is relatively difficult for both, and it is very difficult to reduce the coating amount, resulting in a relatively high coating cost.

[0105] Example 7

[0106] Papermaking of the plastic film base paper: Take about 500 g of oven-dry weight of the bio-mechanical pulp, and beat it with a Valley beater for about 20 minutes, with the beating degree of about 40° SR. After the beating, filter out the vast majority of the water with a pulp bag, put it into a 5°C low-temperature refrigerator for 24 hours to balance the moisture, and measure the solid content.

[0107] Mix 1.88 g of oven-dry pulp and papermaking aids including 1% CPAM dry strength agent, 2.5% PAE wet strength agent, 0.5% AKD sizing agent, and 0.1% retention aid based on the weight of the oven-dry pulp in a refiner, and refine it at 10,000 revolutions to completely disperse the fibers. After refining, send the pulp to a paper machine to obtain a plastic film base paper of 60 g / m 2 ².

[0108] Coating experiment of the plastic film base paper: First, prepare a 7% aqueous solution of cationic starch, and then add 10% sodium hydroxide based on the mass of the starch. Stir mechanically at 40°C for 30 minutes at 10,000 revolutions to obtain the gelatinized cationic starch. Fix the plastic film base paper, and evenly coat the gelatinized cationic starch on both sides of the plastic film base paper with a 10-μm linear coating rod, and dry it at 80°C for 10 minutes. Take it out, and continue to coat polyurethane on the starch layer on both sides with a 4-μm linear coating rod, and dry it at 110°C for 10 minutes to obtain the plastic film paper. The properties of the prepared plastic film paper are shown in Table 7.

[0109] Table 7 Properties of the plastic film paper

[0110]

[0111] The Cobb water resistance of the plastic film paper 120 is 8.6 g / m 2 ², showing excellent hydrophobic properties, 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.

[0112] The water vapor transmission rate of the plastic film paper is 683 g / m 2· 24 hours, it is increased by 424% compared with the original film paper. Through the coating process, good water vapor barrier performance is given to the film paper, which can effectively prevent the loss of water in the soil and crops, achieving the effect of increasing production and efficiency.

[0113] Physical strength index of the film paper: The tearing index is 8.3 mN·m 2 / g, the burst resistance index is 2.48 kPa·m 2 / g, the dry tensile index is 35.6 N·m / g, and the wet tensile index is 26.7 N·m / g. The above four test results all meet the requirements for laying in the greenhouse. Among them, the wet tensile index reaches 75% of the dry tensile index and is increased by 556% compared with the original paper, indicating that even in an environment with high humidity in the greenhouse, the bio-mechanical pulp film paper can be used for a long time.

[0114] The light transmittance of the film paper is 3.9%, which can effectively inhibit the growth and development of weeds, so as to achieve the purpose of inhibiting weed growth in the area covered by the film paper.

[0115] Example 8

[0116] Manufacture of the original film paper: Take about 500 g of oven-dry weight of bio-mechanical pulp, beat it with a Valley beater for about 20 minutes, the beating degree is about 40°SR. After the beating is completed, filter out the vast majority of water with a pulp bag, put it into a 5°C low-temperature refrigerator for 24 hours to balance the moisture, and measure the solid content.

[0117] Mix 1.88 g of oven-dry pulp and papermaking additives of 1% CPAM dry strength agent, 2.5% PAE wet strength agent, 0.5% AKD sizing agent and 0.1% retention aid based on the weight percentage of the oven-dry pulp in a refiner, and defibrate at 10,000 revolutions to completely disperse the fibers. After defibration, send the pulp to a paper machine to obtain a 60 g / m 2 original film paper.

[0118] Coating experiment of the original film paper: First, prepare a 7% aqueous solution of cationic starch, and then add 10% sodium hydroxide based on the mass of the starch. Stir mechanically at 10,000 revolutions for 30 minutes at 40°C to obtain the gelatinized cationic starch.

[0119] Fix the original film paper, and evenly coat the gelatinized cationic starch on both the front and back sides of the original film paper with a 10 μm linear coating rod, and dry it at 80°C for 10 minutes.

[0120] Take it out, and continue to coat the acrylic resin on the starch layer on both the front and back sides with a 4 μm linear coating rod, and dry it at 110°C for 10 minutes to obtain.

[0121] The performance of the prepared film paper is shown in Table 8.

[0122] Table 8 Performance of the film paper

[0123]

[0124] The water resistance Cobb of the plastic film paper 120 is 18.7 g / m 2 , with certain hydrophobic properties, which is beneficial to extend the service life of the plastic film paper in a humid environment.

[0125] The water vapor transmission rate of the plastic film paper is 734 g / m 2 ·24h, which is 394% higher than that of the original plastic film paper. By coating with acrylic resin, the water vapor barrier performance of the plastic film paper is still lower than 800 g / m 2 ·24h, and the cost is lower than that of polyurethane.

[0126] The physical strength index of the plastic film paper: the tearing index is 7.3 mN·m 2 / g, the bursting resistance index is 2.27 kPa·m 2 / g, the dry tensile index is 44.7 N·m / g, and the wet tensile index is 20.7 N·m / g. The above four test results all meet the requirements for laying in the greenhouse. Among them, the wet tensile index reaches 46% of the dry tensile index, and it is 431% higher than that of the original paper. Compared with Example 1, Example 2 shows a higher dry tensile index.

[0127] The light transmittance of the plastic film paper is 4.5%, which can still effectively inhibit the growth and development of weeds and achieve the purpose of weed control.

[0128] Comparative Example 1

[0129] Manufacture of the original plastic film paper: Take about 500 g of air-dry weight of bio-mechanical pulp, beat it with a Valley beater, the beating time is about 20 min, the beating degree is about 40°SR. After the beating is completed, filter out the vast majority of water with a pulp bag, put it into a 5°C low-temperature refrigerator for 24 h to balance the moisture, and measure the solid content.

[0130] Mix 1.88 g of air-dry pulp and papermaking additives including 1% CPAM dry strength agent, 2.5% PAE wet strength agent, 0.5% AKD sizing agent and 0.1% retention aid based on the weight of the air-dry pulp in a repulper, and repulp at 10,000 revolutions to completely disperse the fibers. After repulping, send the pulp to a paper machine to obtain the original plastic film paper with a basis weight of 60 g / m 2 .

[0131] Coating experiment of the original plastic film paper: First, prepare a 7% aqueous solution of cationic starch, and then add 10% sodium hydroxide based on the mass of the starch. Stir mechanically at 40°C for 30 min at 10,000 revolutions to obtain gelatinized cationic starch. Fix the original plastic film paper, and evenly coat the gelatinized cationic starch on both sides of the original plastic film paper with a 10-μm linear coating rod, and dry it at 80°C for 10 min.

[0132] The properties of the prepared plastic mulch paper are shown in Table 9.

[0133] Table 9 Properties of the plastic mulch paper

[0134]

[0135] 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 can have various changes and modifications. 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 plastic film paper for greenhouse, characterized in that: It includes the following steps: After defibrating the wheat straw biopulping, beating treatment is carried out, and the beating degree is 35-40 °SR to obtain a slurry; After fully mixing the slurry with a papermaking aid, papermaking is carried out to obtain a base paper for the plastic film; Uniformly coat the base paper for the plastic film on one side or both sides with gelatinized cationic starch or gelatinized soybean oil modified starch, and dry; when gelatinizing, the mass percentage of the cationic starch aqueous solution is 3-10%; the mass percentage of starch in the soybean oil modified starch is 2.5-10%; Then uniformly coat a polyurethane or acrylic resin coating on one side or both sides, and obtain the product after drying; The biopulping is first pretreated with biological enzymes and then prepared by mechanical pulping, wherein the biological enzymes are composed of a composite of pectinase, lipase and xylanase; The preparation method of the gelatinized cationic starch is: after adjusting the cationic starch aqueous solution to alkaline, heating it to 40-50 °C and stirring for 20-40 min to obtain it; The papermaking aid includes cationic polyacrylamide or cationic starch or chitosan accounting for 0.5%-3% of the absolute dry pulp mass, polyamide polyamine epichlorohydrin accounting for 1.5%-3% of the absolute dry pulp mass, alkyl ketene dimer or aluminum sulfate accounting for 0.5%-2% of the absolute dry pulp mass, and cationic / anionic polyacrylamide or cationic / anionic starch accounting for 0.1%-0.3% of the absolute dry pulp mass.

2. The preparation method of the plastic film paper for greenhouse according to claim 1, characterized in that: It further includes the step of adding 0-40% mass percentage of waste corrugated paper pulp or wheat straw pulp to the wheat straw biopulping, and the addition ratio of the waste corrugated paper pulp or wheat straw pulp is not 0.

3. The preparation method of the plastic film paper for greenhouse according to claim 1, characterized in that: The papermaking aid includes cationic polyacrylamide or cationic starch or chitosan accounting for 1%-2% of the absolute dry pulp mass, polyamide polyamine epichlorohydrin accounting for 2%-3% of the absolute dry pulp mass, alkyl ketene dimer or aluminum sulfate accounting for 0.5%-1% of the absolute dry pulp mass, and cationic / anionic polyacrylamide or cationic / anionic starch accounting for 0.1%-0.2% of the absolute dry pulp mass.

4. The preparation method of the plastic film paper for greenhouse according to claim 3, characterized in that: The papermaking aid includes cationic polyacrylamide accounting for 1%-2% of the absolute dry pulp mass, polyamide polyamine epichlorohydrin accounting for 2%-3% of the absolute dry pulp mass, and alkyl ketene dimer accounting for 0.5%-1% of the absolute dry pulp mass.

5. The preparation method of the plastic film paper for greenhouse according to claim 1, characterized in that: The mass percentage of the cationic starch aqueous solution is 3-10%; In the cationic starch aqueous solution, the mass percentage of sodium hydroxide is 8%-15%.

6. The preparation method of the plastic film paper for greenhouse according to claim 1, characterized in that: The preparation method of the soybean oil modified starch is: adding soybean oil and sodium carbonate to the dimethyl sulfoxide solution of starch to obtain a mixed solution, heating it to 110-150 °C, and the heating time is 1-3 h to carry out hydrophobic modification on the starch.

7. The preparation method of the plastic film paper for greenhouse according to claim 6, characterized in that: In the mixed solution, the mass percentage of starch is 2.5 - 10%; the mass percentage of soybean oil is 8 - 12%; the mass percentage of sodium carbonate is 13 - 17%.

8. According to the method for preparing the greenhouse plastic film paper described in claim 1, it is characterized in that: The coating method of the gelatinized cationic starch or gelatinized soybean oil modified starch is as follows: coating is carried out on the surface of the original plastic film paper with a 10 μm linear coating rod, and it can be used after drying.

9. According to the method for preparing the greenhouse plastic film paper described in claim 8, it is characterized in that: The single-sided coating amount of gelatinized cationic starch or gelatinized soybean oil-modified starch is 1.5 - 2 g / m 2 , and the double-sided coating amount is 3 - 4 g / m 2 .

10. According to the method for preparing the greenhouse plastic film paper described in claim 1, it is characterized in that: The coating method of the polyurethane or acrylic resin coating is as follows: coating is carried out on the surface of the gelatinized cationic starch or gelatinized modified starch coating with a 4 μm linear coating rod, and it is obtained after drying.

11. According to the method for preparing the greenhouse plastic film paper described in claim 1, it is characterized in that: The single-sided coating amount of polyurethane is 1.5 - 2 g / m 2 , and the double-sided coating amount is 3 - 4 g / m 2 .

12. According to the method for preparing the greenhouse plastic film paper described in claim 11, it is characterized in that: The single-sided coating amount of the acrylic resin is 2.5 - 3 g / m 2 , and the double-sided coating amount is 5 - 6 g / m 2 .

13. According to the method for preparing the greenhouse plastic film paper described in claim 1, it is characterized in that: The basis weight of the mulch paper is 60 - 70 g / m 2 .

14. A greenhouse plastic film paper, it is characterized in that: It is prepared by the preparation method described in any one of claims 1 - 13.

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