Salix psammophila-wheat straw degradable mulch film and preparation method thereof

Abstract

The present invention provides a salix psammophila-wheat straw degradable mulch film and a preparation method thereof, and belongs to the field of agriculture. The method of the present invention comprises: salix psammophila and wheat straw are respectively subjected to alkali solution cooking, and sieving, cleaning and grinding to obtain salix psammophila fiber pulp and wheat straw pulp; the salix psammophila fiber pulp and wheat straw pulp are mixed in proportion to obtain mixed paper pulp; after adding water, dry strength agent, wet strength agent and sizing agent to the mixed paper pulp, the mixed paper pulp is formed into wet paper, and the wet paper is dried into film to obtain salix psammophila-wheat straw degradable mulch film. The present invention adopts salix psammophila fiber composite wheat straw fiber to prepare mulch film, and compared with the common straw fiber film on the market, while improving the mechanical properties of the paper-based mulch film, the sustainable utilization of salix psammophila resources is realized, and the present invention has low energy consumption, simple production process flow, abundant raw material sources, and is conducive to large-scale production.

Description

Technical Field

[0001] The invention belongs to the field of agriculture, and in particular relates to a Salix psammophila-wheat straw degradable mulch film and a preparation method thereof. Background Art

[0002] According to relevant literature statistics, the global agricultural mulch film usage is large every year, and most of the common mulch films used are mainly composed of polyethylene (PE) or polyvinyl chloride (PVC), which have high component stability and long half-life, and can remain in the soil for hundreds of years, causing persistent pollution. Composite fiber paper-based mulch can be naturally degraded in the soil and does not pollute the environment. Therefore, the research and development of composite fiber paper-based mulch has broad prospects and great research value.

[0003] In theory, plant fiber mulch is a green, environmentally friendly, degradable mulch. It is usually made of plant fiber as raw material, with additives such as wet strength agent, preservative and transparent agent added to the pulp, and the base paper is made using papermaking technology, and then processed to make the mulch. According to reports, there are research units currently developing and researching paper mulch, but most of them are in the experimental stage. Due to the immaturity of the technology, its heat preservation and moisture retention effect is not obvious, its degradability and degradation time are uncontrollable, and its mechanical properties do not meet the relevant strength requirements of plastic mulch. Problems such as dry and wet strength, breaking strength and degradability of mulch products still need to be solved. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method for preparing a Salix psammophila-wheat straw degradable mulch film, and the prepared paper-based mulch film has good mechanical properties and hydrophobicity.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a Salix psammophila-wheat straw degradable mulch film, comprising the following steps:

[0007] Salix psammophila and wheat straw are respectively cooked with alkali solution, and Salix psammophila fiber pulp and wheat straw pulp are obtained after pulp screening, cleaning and grinding; the Salix psammophila fiber pulp and wheat straw pulp are mixed in proportion to obtain mixed paper pulp; water, dry strength agent, wet strength agent and sizing agent are added to the mixed paper pulp, and then papermaking and molding are obtained to obtain wet paper, and the wet paper is dried to form a film to obtain Salix psammophila-wheat straw degradable mulch film.

[0008] Preferably, the alkali solution cooking method includes: mixing Salix psammophila: water: alkali according to 150-250g: 650-900mL: 65-95g, and high-pressure cooking at 180-220°C for 1.5-2.5h; mixing wheat straw: water: alkali according to 80-120g: 300-500mL: 10-20g, and high-pressure cooking at 150-190°C for 30-50min.

[0009] Preferably, the base comprises NaOH, Ca(OH)2, KOH or Na2CO3.

[0010] Preferably, the pulp screening speed is 690-700 rpm, and the pulp supernatant is washed until the pH value is 6.8-7.2; and the pulping concentration is 25-35%.

[0011] Preferably, the Salix psammophila fiber pulp and the wheat straw pulp are mixed in a mass ratio of 6-8:2-4.

[0012] Preferably, the dry weight of the mixed pulp is 55-65 g / m 2 The amount of water added is 300 to 700 times the dry weight of the mixed pulp.

[0013] Preferably, based on the mass percentage of the absolute dry slurry, the addition amount of the dry strength agent is 0.5-2.5%, the addition amount of the wet strength agent is 0.5-2.5%, and the addition amount of the sizing agent is 0.2-1.5%.

[0014] Preferably, the dry strength agent is CPAM, the wet strength agent is PAE, and the sizing agent is AKD.

[0015] Preferably, the drying method is vacuum high-temperature drying, the temperature is 90-110° C., the vacuum pressure is 8-14 MPa, and the drying time is 3-6 min.

[0016] The present invention also provides a Salix psammophila-wheat straw degradable mulch film prepared by the above preparation method.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention combines Salix psammophila fiber and wheat straw fiber to prepare a paper-based film, so that the two have a synergistic effect, greatly enhancing the mechanical strength of the paper-based film, and having high tensile strength, tear resistance and high hydrophobicity. The dry tensile strength of the film is ≥2.55 kN / m, the wet tensile strength is ≥0.45 kN / m, the tear resistance is ≥540 mN, and the contact angle range is 90.1° to 104.2°.

[0019] The Salix psammophila-wheat straw degradable mulch film prepared by the invention plays a role in increasing temperature and entropy in the soil, effectively maintains the soil moisture content and temperature, and can effectively maintain the soil moisture content at 20-30% and the soil temperature range at 30-35°C.

[0020] The method of the present invention can realize the sustainable utilization of Salix psammophila resources, and the present invention has low energy consumption, simple production process flow, abundant raw material sources, and is conducive to large-scale production. DETAILED DESCRIPTION

[0021] The present invention provides a method for preparing a Salix psammophila-wheat straw degradable mulch film, comprising the following steps:

[0022] Salix psammophila and wheat straw are respectively cooked with alkali solution, and Salix psammophila fiber pulp and wheat straw pulp are obtained after pulp screening, cleaning and grinding; the Salix psammophila fiber pulp and wheat straw pulp are mixed in proportion to obtain mixed paper pulp; water, dry strength agent, wet strength agent and sizing agent are added to the mixed paper pulp, and then papermaking and molding are obtained to obtain wet paper, and the wet paper is dried to form a film to obtain Salix psammophila-wheat straw degradable mulch film.

[0023] The present invention combines Salix tamarisk fiber and wheat straw fiber to prepare paper-based membranes, so that the two have a synergistic effect. By taking advantage of the good fiber formability, high aspect ratio and rich carbon content of Salix tamarisk fibers, the tear resistance of the membrane can be effectively improved on the basis of the wheat straw fiber membrane, and the strength and flexibility of the paper-based membrane can be further improved, thereby greatly enhancing the mechanical strength of the paper-based membrane, while also playing a role in increasing temperature and entropy, effectively maintaining the moisture content and temperature of the soil.

[0024] In the present invention, alkali solution is added to the pretreated Salix psammophila raw material, and the raw material is cooked in a high-pressure cooking pot. The Salix psammophila: water: alkali are mixed according to 150-250g: 650-900mL: 65-95g, and the ratio of Salix psammophila: water: alkali is preferably 200g: 800mL: 80g. The pretreatment method of the Salix psammophila raw material of the present invention is peeling the Salix psammophila; the mass of the Salix psammophila is the absolute dry raw material amount, the cooking temperature is 180-220°C, preferably 200°C, and the cooking time is 1.5-2.5h, preferably 2h. The present invention preferably keeps the cooked Salix psammophila warm for 120-180min, more preferably 150min.

[0025] In the present invention, alkali solution is added to the pretreated wheat straw raw material, and the raw material is cooked in a high-pressure cooking pot. The wheat straw: water: alkali is mixed according to 80-120g: 300-500mL: 10-20g, and the ratio of the wheat straw: water: alkali is preferably 100g: 400mL: 15g. The pretreatment method of the wheat straw raw material of the present invention is to screen out weeds, soil and wheat ears; the mass of the wheat straw is the absolute dry raw material amount, the cooking temperature is 150-190°C, preferably 170°C, and the cooking time is 30-50min, preferably 40min. The present invention preferably keeps the cooked wheat straw warm for 60-120min, more preferably 80min.

[0026] The base of the present invention includes NaOH, Ca(OH)2, KOH or Na2CO3.

[0027] The present invention washes the two pulps obtained by cooking in a pulp screening machine respectively. The pulp screening speed is 690-700 rpm. When the pH value of the pulp supernatant is 6.8-7.2, the pulp screening is completed. The pH value of the pulp supernatant is preferably 7.

[0028] The present invention refines the cleaned Salix psammophila and wheat straw respectively, and the refining concentration is 25-35%, preferably 30%. The present invention obtains Salix psammophila fiber pulp with a beating degree of 35-45°SR and wheat straw pulp with a beating degree of 45-55°SR respectively through refining, and the beating degree of the obtained Salix psammophila fiber pulp is preferably 40°SR, and the beating degree of the wheat straw fiber pulp is preferably 50°SR.

[0029] The present invention mixes the refined Salix psammophila fiber pulp and the wheat straw pulp in a mass ratio of 6-8:2-4 to obtain a mixed pulp, and the mixing ratio is preferably 7:3. The present invention adds water to the mixed pulp, and based on the dry weight of the mixed pulp, the amount of water added is 300-700 times, preferably 400-600 times, and more preferably 500 times the dry weight of the mixed pulp. The dry weight of the mixed pulp of the present invention is 55-65g / m 2 , preferably 60g / m 2 The water is added in a standard defibrator and sheet former.

[0030] The present invention continues to add dry strength agent, wet strength agent and sizing agent to the mixed pulp, and forms wet paper. The dry strength agent is used to increase the dry strength, the wet strength agent is used to increase the wet strength, and the sizing agent is used to increase the water resistance. In terms of the mass percentage of the absolute dry pulp, the addition amount of the dry strength agent is 0.5-2.5%, preferably 1-2%, and more preferably 1.5%; the addition amount of the wet strength agent is 0.5-2.5%, preferably 1-2%, and more preferably 1.5%; the addition amount of the sizing agent is 0.2-1.5%, preferably 0.5-1.2%, and more preferably 1%. The dry strength agent is CPAM, the wet strength agent is PAE, and the sizing agent is AKD.

[0031] The present invention dries wet paper into film to obtain a Salix psammophila-wheat straw degradable mulch film. The drying method is vacuum high-temperature drying, the temperature is 90-110°C, preferably 100°C, the vacuum pressure is 8-14MPa, preferably 10-12MPa, and the drying time is 3-6min, preferably 4-5min.

[0032] The present invention also provides a Salix psammophila-wheat straw degradable mulch film prepared by the above method, wherein the mulch film has a dry tensile strength of ≥2.55 kN / m, a wet tensile strength of ≥0.45 kN / m, a tear strength of ≥540 mN, and a contact angle range of 90.1° to 104.2°.

[0033] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] A method for preparing a Salix psammophila-wheat straw degradable mulch film:

[0036] (1) Cooking: The tamarisk and wheat were subjected to high-pressure cooking respectively; 800 mL of water and 80 g of sodium hydroxide were added to 200 g of the treated tamarisk raw material, and the mixture was heated to 200 °C in a high-pressure cooking pot and then steamed for 2 h; 400 g of water and 15 g of sodium hydroxide were added to 100 g of the treated wheat straw, and the mixture was heated to 170 °C in a high-pressure cooking pot and then steamed for 40 min.

[0037] (2) Screening: At a screening speed of 700 rpm, the cooked Salix psammophila fiber pulp and wheat straw fiber pulp were washed separately until the pH value of the pulp supernatant reached 7.

[0038] (3) Pulping: The screened Salix psammophila and wheat straw were pulped separately at a pulping concentration of 30% to obtain Salix psammophila fiber pulp and wheat straw pulp, respectively; the obtained Salix psammophila fiber pulp had a beating degree of 40°SR, and the obtained wheat straw fiber pulp had a beating degree of 50°SR.

[0039] (4) Pulping: Mix 70% of Salix psammophila fiber pulp and 30% of wheat straw pulp, and add 300 to 700 times the dry weight of the mixed pulp of water. The dry weight of the mixed pulp is 60 g / m 2 .

[0040] (5) Adding auxiliary agents: After adding 1.5% cationic polyacrylamide (CPAM), 1.5% polyamide epichlorohydrin (PAE), and 0.4% alkyl ketene dimer (AKD) in a mass percentage relative to the absolute dry pulp, the mixed pulp is dissociated. Water is added in a standard fiber disintegrator and a paper sheet forming machine, and the amount of water added is 600 times the dry weight of the mixed pulp.

[0041] (6) Wet paper forming: The pulp obtained in step (5) is paper-formed to obtain wet paper.

[0042] (7) Film formation: vacuum high-temperature drying is performed at a temperature of 100° C. and a vacuum pressure of 12 MPa for 5 min to form a film on the wet paper.

[0043] Test the obtained mulch paper:

[0044] A 5×20mm sample was cut and tested using an INSTRON5948 micromechanical testing machine with the parameters set to a clamp spacing of 50mm and a loading speed of 20mm / min. At this time, the test showed that the dry tensile strength of the mulch paper was 3.24KN / m.

[0045] A sample of 63×50 mm was cut and tested using a LGD-SL1000 tear strength tester, and the tear strength of the mulch paper was found to be 600 mN.

[0046] A 5×20mm sample was cut and completely immersed in distilled water for 2h. Then a micromechanical testing machine was used with the parameters set to a clamp spacing of 50mm and a loading speed of 20mm / min. At this time, the wet tensile strength of the mulch paper was tested to be 1.27KN / m.

[0047] A sample of 20×20 mm was cut and then tested using a JY-PHa interfacial tension tester. At this time, the contact angle of the mulch paper was tested to be 112.95°.

[0048] Example 2

[0049] The difference between this embodiment and embodiment 1 is that in step (5), 1% cationic polyacrylamide (CPAM), 1% polyamide epichlorohydrin (PAE), and 0.5% alkyl ketene dimer (AKD) are added in percentage by weight relative to the absolute dry slurry.

[0050] The test method of the mulch film described in Example 1 yielded the following results: the dry tensile strength of the mulch film paper was 3.07 KN / m, the tear strength of the mulch film paper was 580 mN, the wet tensile strength of the mulch film paper was 1.10 KN / m, and the contact angle of the mulch film paper was 110.6°.

[0051] Example 3

[0052] The difference between this embodiment and embodiment 1 is that in step (4), 60% of Salix psammophila fiber pulp and 40% of wheat straw pulp are mixed.

[0053] The test method for the mulch film described in Example 1 yielded the following results: the dry tensile strength of the mulch film paper was 2.59 KN / m, and the tear strength of the mulch film paper was 480 mN.

[0054] Example 4

[0055] The difference between this embodiment and embodiment 1 is that in step (4), 80% of Salix psammophila fiber pulp and 20% of wheat straw pulp are mixed.

[0056] The test method for the mulch film described in Example 1 yielded the following results: the dry tensile strength of the mulch film paper was 2.36 KN / m, and the tear strength of the mulch film paper was 560 mN.

[0057] Comparative Example 1

[0058] The difference between this comparative example and Example 1 is that only 1% cationic polyacrylamide (CPAM) is added in step (5).

[0059] The test method of the mulch film described in Example 1 yielded the following results: the dry tensile strength of the mulch film paper was 2.71 KN / m, the tear strength of the mulch film paper was 580 mN, the wet tensile strength of the mulch film paper was 1.178 KN / m, and the contact angle of the mulch film paper was 90.6°.

[0060] Comparative Example 2

[0061] The difference between this comparative example and Example 1 is that only 1% of polyamide epichlorohydrin (PAE) is added in step (5).

[0062] The test method of the mulch film described in Example 1 yielded the following results: the dry tensile strength of the mulch film paper was 3.07 KN / m, the tear strength of the mulch film paper was 320 mN, the wet tensile strength of the mulch film paper was 1.10 KN / m, and the contact angle of the mulch film paper was 94.2°.

[0063] Comparative Example 3

[0064] The difference between this comparative example and Example 1 is that only 0.5% of alkyl ketene dimer (AKD) is added in step (5).

[0065] The test method of the mulch film described in Example 1 yielded the following results: the dry tensile strength of the mulch film paper was 1.92 KN / m, the tear strength of the mulch film paper was 320 mN, the wet tensile strength of the mulch film paper was 0.420 KN / m, and the contact angle of the mulch film paper was 110.6°.

[0066] Comparative Example 4

[0067] The difference between this comparative example and Example 1 is that in step (4), no wheat straw pulp is added, and 100% of Salix psammophila fiber pulp is added.

[0068] The test method for the mulch film described in Example 1 yielded the following results: the dry tensile strength of the mulch film paper was 2.45 KN / m, the tear strength of the mulch film paper was 640 mN, and the mulch film paper did not have wet tensile strength and hydrophobic properties.

[0069] Comparative Example 5

[0070] The difference between this comparative example and Example 1 is that in step (4), no Salix psammophila fiber pulp is added, and 100% wheat straw pulp is added.

[0071] The test method of the mulch film described in Example 1 yielded the following results: the dry tensile strength of the mulch film paper was 4.98 KN / m, the tear strength of the mulch film paper was 240 mN, and the mulch film paper did not have wet tensile strength and hydrophobic properties.

[0072] Comparative Example 6

[0073] The difference between this comparative example and Example 1 is that in step (4), 50% of Salix psammophila fiber pulp and 50% of wheat straw pulp are mixed.

[0074] The test method for the mulch film described in Example 1 yielded the following results: the dry tensile strength of the mulch film paper was 2.53 KN / m, and the tear strength of the mulch film paper was 460 mN.

[0075] Comparative Example 7

[0076] The difference between this comparative example and Example 1 is that in step (4), 40% of Salix psammophila fiber pulp and 60% of wheat straw pulp are mixed.

[0077] The test method for the mulch film described in Example 1 yielded the following results: the dry tensile strength of the mulch film paper was 2.58 KN / m, and the tear strength of the mulch film paper was 440 mN.

[0078] Comparative Example 8

[0079] The difference between this comparative example and Example 1 is that in step (4), 30% of Salix psammophila fiber pulp and 70% of wheat straw pulp are mixed.

[0080] The test method for the mulch film described in Example 1 yielded the following results: the dry tensile strength of the mulch film paper was 2.63 KN / m, and the tear strength of the mulch film paper was 400 mN.

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a Salix psammophila-wheat straw degradable mulch film, characterized in that: The following steps are involved: The salix psammophila and wheat straw are respectively boiled with alkali solution, and the salix psammophila fiber pulp and wheat straw pulp are obtained after pulp screening, cleaning and grinding; the salix psammophila fiber pulp and wheat straw pulp are mixed in proportion to obtain mixed paper pulp; water, dry strength agent, wet strength agent and sizing agent are added to the mixed paper pulp, and then the mixed paper pulp is formed into wet paper, and the wet paper is dried to form a film to obtain a salix psammophila-wheat straw degradable mulch film; The alkali liquor cooking method Includes: Salix: Water: alkali is mixed according to 150-250g: 650-900mL: 65-95g, and high pressure steamed at 180-220℃ for 1.5-2.5h; Wheat straw: Water: alkali is mixed in the ratio of 80-120 g: 300-500 mL: 10-20 g, and high pressure steamed at 150-190° C. for 30-50 min; the alkali includes NaOH, Ca(OH)2, KOH or Na2CO3; The Salix psammophila fiber pulp and the wheat straw pulp are mixed in a mass ratio of 6-8:2-4; Calculated by the mass percentage of the absolute dry slurry, the addition amount of the dry strength agent is 0.5-2.5%, the addition amount of the wet strength agent is 0.5-2.5%, and the addition amount of the sizing agent is 0.2-1.5%; the dry strength agent is CPAM, the wet strength agent is PAE, and the sizing agent is AKD.

2. The preparation method according to claim 1, characterized in that: The screening speed is 690-700 rpm, and the pH value of the pulp supernatant is 6.8-7.2; the pulping concentration is 25-35%.

3. The preparation method according to claim 1, characterized in that: The dry weight of the mixed pulp is 55-65 g / m 2 The amount of water added is 300 to 700 times the dry weight of the mixed pulp.

4. The preparation method according to claim 1, characterized in that: The drying method is vacuum high-temperature drying, the temperature is 90-110° C., the vacuum pressure is 8-14 MPa, and the drying time is 3-6 minutes.

5. The Salix psammophila-wheat straw degradable mulch film prepared by the preparation method according to any one of claims 1 to 4.