Wood pulp fiber modified polylactic acid coated paper and method of making the same

Abstract

The application discloses wood pulp fiber modified polylactic acid coated paper, which is composed of the following components in percentage by weight: 0.06%-0.55% wood pulp board, 87.29%-87.72% N,N-dimethylformamide, 2.81%-2.82% A4 paper and 9.35%-9.4% polylactic acid, and the sum of the percentage by weight of the above components is 100%. The modified polylactic acid coated paper solves the problems of poor hydrophobicity and barrier property and poor mechanical property of the existing paper. The application further discloses a preparation method of the wood pulp fiber modified polylactic acid coated paper.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite material preparation and functional paper preparation, in particular to wood pulp fiber modified polylactic acid coated paper, and also relates to a preparation method of the wood pulp fiber modified polylactic acid coated paper. BACKGROUND

[0002] With the improvement of people's environmental awareness, environmental protection, energy saving and emission reduction have become the focus of the whole human being. Based on this, the traditional non-degradable petroleum-based plastic is facing severe challenges, and at the same time, "using paper instead of plastic" has become an important trend in the packaging field. Paper-based materials are green and environmentally friendly materials formed by interweaving and overlapping fibers, and have the characteristics of wide source, low price, renewable and degradable, and are widely used in various fields. However, compared with plastic products, the tensile strength of paper is low, and the natural cellulose paper is rich in hydrophilic hydroxyl and carboxyl groups, which leads to strong hydrophilicity and hygroscopicity of the natural cellulose paper, which seriously limits the application field of the paper material. In addition, the surface of the paper-based material is loose and porous, and small molecules of water / oil can easily penetrate and wet the fibers through the pores, resulting in poor barrier property of the paper-based material, which cannot meet the barrier function requirements of the packaging material.

[0003] Polylactic acid is a completely degradable material, and its degradation products are carbon dioxide and water, which can realize green cycle in nature through plant photosynthesis, and is a recognized environmentally friendly material. Polylactic acid has high transparency and high gloss, has high biocompatibility and excellent mechanical properties, and is widely used as a substitute for petroleum-based plastics in packaging, agriculture, fiber textiles, medical and engineering plastics and other fields. In addition, polylactic acid is a hydrophobic crystalline polymer composed of aliphatic polyester, and the material surface has strong hydrophobicity due to the lack of hydrophilic groups in its structure, and the space shielding effect of the methyl side group (-CH3) of polylactic acid, which makes it have high water resistance. Polylactic acid has certain barrier effect on oxygen and water vapor, but it is not excellent, and barrier property is an important factor to measure the quality of packaging materials, such as moisture permeability and oxygen permeability. Therefore, for high-performance polylactic acid packaging materials, it is also necessary to modify and composite to improve the performance of the material. SUMMARY

[0004] The first object of the present application is to provide wood pulp fiber modified polylactic acid coated paper, which solves the problems of poor hydrophobicity and barrier property and poor mechanical property of the existing paper.

[0005] The second object of the present application is to provide a preparation method of wood pulp fiber modified polylactic acid coated paper, which aims to develop a functional paper production route using a simple process.

[0006] The first technical solution of the present application is wood pulp fiber modified polylactic acid coated paper, which is composed of the following components by weight percentage: 0.06% to 0.55% wood pulp board, 87.29% to 87.72% N,N-dimethylformamide, 2.81% to 2.82% A4 paper, and 9.35% to 9.4% polylactic acid, and the sum of the weight percentages of the above components is 100%.

[0007] The present application is also characterized in that:

[0008] The wood pulp board is waste white cardboard, broadleaf wood pulp board, or coniferous wood pulp board.

[0009] The second technical solution of the present application is a wood pulp fiber modified polylactic acid coated paper preparation method, which comprises the following steps:

[0010] Step 1, the following components are weighed by weight percentage: 0.06% to 0.55% wood pulp board, 87.29% to 87.72% N,N-dimethylformamide, 2.81% to 2.82% A4 paper, and 9.35% to 9.4% polylactic acid, and the sum of the weight percentages of the above components is 100%;

[0011] Step 2, the wood pulp board is pretreated;

[0012] Step 3, wood pulp fiber / polylactic acid composite material is prepared;

[0013] Step 4, wood pulp fiber modified polylactic acid coated paper is prepared.

[0014] The present application is also characterized in that:

[0015] In step 1, the wood pulp board is waste white cardboard, broadleaf wood pulp board, or coniferous wood pulp board.

[0016] Step 2 is specifically:

[0017] Step 2.1, the weighed wood pulp board is crushed into 15mm×4mm to 20mm×10mm fragments, soaked in deionized water for 30min to 60min, and the mass ratio of wood pulp board to deionized water is 1:30;

[0018] Step 2.2, the soaked wood pulp board in step 2.1 is put into a paper pulp disintegrating machine and is beaten and disintegrated at a speed of 8000r / min to 10000r / min to obtain wood pulp fiber;

[0019] Step 2.3, the wood pulp fiber obtained in step 2.2 is dried in an electric heating air drying oven at 70℃ to 80℃ for 18h to 24h;

[0020] Step 2.4, dry the wood pulp fibers obtained in step 2.3 in a pulverizer at a speed of 27000-29000 r / min for 10-30 s to obtain refined wood pulp fibers, and the refined wood pulp fibers are packaged in a sealed bag for standby.

[0021] Step 3 is specifically:

[0022] Step 3.1, the wood pulp fibers obtained in step 2.4 are added to N,N-dimethylformamide, and an ultrasonic cell pulverizer with a power of 900 W is used to ultrasonically disperse the wood pulp fibers for 3-5 min at a power of 35%-40% to obtain a wood pulp fiber dispersion;

[0023] Step 3.2, add polylactic acid to the wood pulp fiber dispersion, heat and stir in a magnetic stirrer at a water bath temperature of 70-80℃ and a stirring speed of 400-500 rpm for 2-3 h to obtain a wood pulp fiber / polylactic acid composite solution.

[0024] Step 4 is specifically:

[0025] Step 4.1, cut the A4 paper into a square with a size of 70mm×70mm-80mm×80mm;

[0026] Step 4.2, pour the wood pulp fiber / polylactic acid composite solution prepared in step 3.2 into a culture dish with a diameter of 100 mm;

[0027] Step 4.3, place the square A4 paper cut in step 4.1 into the culture dish containing the wood pulp fiber / polylactic acid composite solution in step 4.2 for 15-30 s of immersion coating;

[0028] Step 4.4, place the A4 paper coated with the wood pulp fiber / polylactic acid composite solution prepared in step 4.3 in a vacuum drying oven at 90-100℃ and dry for 1.5-2 h to obtain wood pulp fiber modified polylactic acid coated paper.

[0029] The beneficial effects of the present application are:

[0030] (1) The wood pulp fiber modified polylactic acid coated paper of the present application solves the problems of poor hydrophobicity and barrier property and poor mechanical property of the existing paper by synthesizing a novel layer-by-layer assembled sandwich structure functional paper through a simple preparation process of physical blending method and dip coating method.

[0031] (2) The method of the present application solves the problems of poor hydrophobicity and barrier property and poor mechanical property of the existing paper by synthesizing a novel layer-by-layer assembled sandwich structure functional paper through a simple preparation process of physical blending method and dip coating method, and provides a way for producing functional paper and lays a certain theoretical research foundation and practical experience for expanding the application range of paper. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a scanning electron microscope image of the wood pulp fiber modified polylactic acid coated paper prepared in Example 4 of the present application;

[0033] Figure 2 is a contact angle diagram of A4 paper, polylactic acid coated paper, polylactic acid coated paper prepared in Example 4 and Example 5 of the present application;

[0034] Figure 3 is a moisture permeability diagram of A4 paper, polylactic acid coated paper, polylactic acid coated paper prepared in Example 4 and Example 5 of the present application;

[0035] Figure 4 is a stress-strain diagram of A4 paper, polylactic acid coated paper, polylactic acid coated paper prepared in Example 2, 3, 4 and 5 of the present application;

[0036] Figure 5 is a folding endurance diagram of A4 paper, polylactic acid coated paper, polylactic acid coated paper prepared in Example 1 and Example 4 of the present application. DETAILED DESCRIPTION

[0037] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0038] The present application provides wood pulp fiber modified polylactic acid coated paper, which is composed of 0.06-0.55% wood pulp board, 87.29-87.72% N,N-dimethylformamide, 2.81-2.82% A4 paper and 9.35-9.4% polylactic acid (relative molecular weight is 11000 g / mol) by weight percentage, and the sum of the weight percentages of the above components is 100%.

[0039] The wood pulp board is waste white cardboard, broadleaf wood pulp board or coniferous wood pulp board.

[0040] The present application also provides a preparation method of wood pulp fiber modified polylactic acid coated paper, which comprises the following steps:

[0041] In step 1, the following components are weighed by weight parts: 0.06-0.55% wood pulp board, 87.29-87.72% N,N-dimethylformamide, 2.81-2.82% A4 paper and 9.35-9.4% polylactic acid, and the sum of the weight percentages of the above components is 100%.

[0042] In step 1, the wood pulp board is waste white cardboard, broadleaf wood pulp board or coniferous wood pulp board.

[0043] In step 2, the wood pulp board is pretreated.

[0044] In step 2, the wood pulp board is pretreated.

[0045] In step 2.1, the weighed wood pulp board is crushed into 15mm*4mm-20mm*10mm fragments, soaked in deionized water for 30-60 min, and the mass ratio of wood pulp board to deionized water is 1:30.

[0046] In step 2.2, the soaked wood pulp board in step 2.1 is put into a paper pulp disintegrating machine and is beaten and disintegrated at a speed of 8000-10000 r / min to obtain wood pulp fibers.

[0047] In step 2.3, the wood pulp fibers obtained in step 2.2 are dried in an electric heating air drying oven at 70-80℃ for 18-24 h.

[0048] In step 2.4, the dried wood pulp fibers in step 2.3 are crushed in a multifunctional crusher at a speed of 27000-29000 r / min for 10-30 s to obtain refined wood pulp fibers, which are packaged with a sealed bag.

[0049] In step 3, a wood pulp fiber / polylactic acid composite material is prepared.

[0050] In step 3, a wood pulp fiber / polylactic acid composite material is prepared.

[0051] Step 3.1, the wood pulp fibers obtained in step 2.4 are added into N,N-dimethylformamide, and an ultrasonic cell crusher with a power of 900 W is used to ultrasonically disperse the wood pulp fibers for 3-5 min at a power of 35%-40% to obtain a wood pulp fiber dispersion;

[0052] Step 3.2, the polylactic acid is added into the wood pulp fiber dispersion, and heated and stirred for 2-3 h in a water bath at a temperature of 70-80 °C and a stirring speed of 400-500 rpm to obtain a wood pulp fiber / polylactic acid composite solution.

[0053] Step 4, preparation of wood pulp fiber modified polylactic acid coated paper.

[0054] Step 4 specifically comprises:

[0055] Step 4.1, the A4 paper is cut into a square with a size of 70 mm x 70 mm-80 mm x 80 mm;

[0056] Step 4.2, the wood pulp fiber / polylactic acid composite solution prepared in step 3.2 is poured into a culture dish with a diameter of 100 mm;

[0057] Step 4.3, the square A4 paper cut in step 4.1 is placed in the culture dish containing the wood pulp fiber / polylactic acid composite solution in step 4.2 for 15-30 s of immersion coating;

[0058] Step 4.4, the A4 paper coated based on the wood pulp fiber / polylactic acid composite solution prepared in step 4.3 is placed in a vacuum drying oven at a temperature of 90-100 °C and dried for 1.5-2 h to obtain wood pulp fiber modified polylactic acid coated paper.

[0059] Wherein: waste white cardboard, collected waste packaging white cardboard; broadleaf wood pulp board, Dalian Yangrun Trading Co., Ltd.; coniferous wood pulp board, Dalian Yangrun Trading Co., Ltd.; N,N-dimethylformamide (DMF), analytical pure, Tianjin Fuyu Fine Chemical Co., Ltd.; polylactic acid (PLA), Shanghai Maikelin Biochemical Technology Co., Ltd.; A4 paper, office A4 paper.

[0060] Example 1

[0061] The wood pulp fiber modified polylactic acid coated paper preparation method comprises the following steps:

[0062] Step 1, the following components are weighed according to the weight parts: 0.06% broadleaf wood pulp board, 87.72% N,N-dimethylformamide, 2.82% A4 paper, and 9.40% polylactic acid, and the sum of the weight percentages of the above components is 100%.

[0063] Step 2, the broadleaf wood pulp board is pretreated;

[0064] Step 2.1, the weighed broadleaf wood pulp board was crushed into 17mm x 6mm fragments and soaked in deionized water for 45min, the mass ratio of wood pulp board to deionized water was 1:30;

[0065] Step 2.2, the soaked broadleaf wood pulp board in step 2.1 was put into a paper pulp disintegrator and was beaten and disintegrated at a speed of 10000r / min to obtain broadleaf wood pulp fibers;

[0066] Step 2.3, the broadleaf wood pulp fibers obtained in step 2.2 were dried in an electric heating air drying oven at 80℃ for 18h;

[0067] Step 2.4, the dried broadleaf wood pulp fibers in step 2.3 were crushed in a crusher at a speed of 28000r / min for 20s to obtain refined wood pulp fibers, which were packaged using a sealed bag.

[0068] Step 3, preparation of wood pulp fiber / polylactic acid composite material;

[0069] Step 3.1, the fibers obtained in step 2.4 were added to N,N-dimethylformamide, and an ultrasonic cell crusher with a power of 900W was used to ultrasonically disperse for 5min at a power of 35% to obtain a broadleaf wood pulp fiber dispersion;

[0070] Step 3.2, polylactic acid was added to the broadleaf wood pulp fiber dispersion, and a magnetic stirrer was used to heat and stir at a water bath temperature of 70℃ and a speed of 500rpm for 3h to obtain a wood pulp fiber / polylactic acid composite solution;

[0071] Step 4, preparation of wood pulp fiber modified polylactic acid coated paper;

[0072] Step 4.1, an A4 paper was cut into a square of 70mm x 70mm;

[0073] Step 4.2, the wood pulp fiber / polylactic acid composite solution prepared in step 3.2 was poured into a culture dish with a diameter of 100mm;

[0074] Step 4.3, the square A4 paper cut in step 4.1 was placed in the culture dish containing the wood pulp fiber / polylactic acid composite solution in step 4.2 to impregnate and coat for 20s;

[0075] Step 4.4, the A4 paper coated based on the wood pulp fiber / polylactic acid composite solution prepared in step 4.3 was placed in a vacuum drying oven at 100℃ and dried for 1.5h to obtain a broadleaf wood pulp fiber modified polylactic acid coated paper.

[0076] Example 2

[0077] A method for preparing wood fiber modified polylactic acid coated paper, comprising the following steps:

[0078] Step 1, the following components are weighed respectively by weight parts: 0.27% of waste white cardboard pulp board, 87.54% of N,N-dimethylformamide, 2.81% of A4 paper, 9.38% of polylactic acid, and the sum of the weight percentages of the above components is 100%.

[0079] Step 2, the waste white cardboard pulp board is pretreated;

[0080] Step 2.1, the weighed waste white cardboard pulp board is crushed into 20mm×10mm fragments, soaked in deionized water for 60min, and the mass ratio of wood pulp board to deionized water is 1:30;

[0081] Step 2.2, the soaked waste white cardboard pulp board in step 2.1 is put into a paper pulp disintegrator and is beaten and disintegrated at a speed of 10000r / min to obtain waste white cardboard fibers;

[0082] Step 2.3, the waste white cardboard fibers obtained in step 2.2 are dried in an electric heating air drying oven at 80℃ for 18h;

[0083] Step 2.4, the dried waste white cardboard fibers in step 2.3 are crushed in a crusher at a speed of 29000r / min for 10s to obtain refined fibers, which are packaged using a sealed bag.

[0084] Step 3, preparing wood fiber / polylactic acid composite material;

[0085] Step 3.1, the fibers obtained in step 2.4 are added to N,N-dimethylformamide, and an ultrasonic cell crusher with a power of 900W is used to ultrasonically disperse for 3min at a power of 40% to obtain a waste white cardboard fiber dispersion;

[0086] Step 3.2, polylactic acid is added to the waste white cardboard fiber dispersion, and heated and stirred in a magnetic stirrer at a water bath temperature of 80℃ and a stirring speed of 400rpm for 2h to prepare a wood fiber / polylactic acid composite solution;

[0087] Step 4, preparing wood fiber modified polylactic acid coated paper;

[0088] Step 4.1, the A4 paper is cut into a square of 75mm×75mm;

[0089] Step 4.2, the wood fiber / polylactic acid composite solution prepared in step 3.2 is poured into a culture dish with a diameter of 100mm;

[0090] Step 4.3, the cut square A4 paper of step 4.1 was placed into the petri dish containing the wood pulp fiber / polylactic acid composite solution in step 4.2 for 30s of dip coating;

[0091] Step 4.4, the wood pulp fiber / polylactic acid composite solution coated A4 paper prepared in step 4.3 was placed in a vacuum drying oven at 90℃ for 2h of drying, obtaining the wood pulp fiber modified polylactic acid coated paper.

[0092] Example 3

[0093] The wood pulp fiber modified polylactic acid coated paper preparation method comprises the following steps:

[0094] Step 1, the following components were weighed according to weight parts: 0.55% of waste white cardboard pulp board, 87.29% of N,N-dimethylformamide, 2.81% of A4 paper, and 9.35% of polylactic acid, the sum of the weight percentages of the above components being 100%.

[0095] Step 2, the waste white cardboard pulp board was pretreated;

[0096] Step 2.1, the weighed waste white cardboard pulp board was crushed into 15mm×4mm fragments and soaked in deionized water for 30min, the mass ratio of the wood pulp board to the deionized water being 1:30;

[0097] Step 2.2, the soaked waste white cardboard pulp board in step 2.1 was placed in a pulp disintegrator and beaten and defibered at a speed of 8000r / min, obtaining waste white cardboard fibers;

[0098] Step 2.3, the waste white cardboard fibers obtained in step 2.2 were dried in an electric heating air drying oven at 70℃ for 24h;

[0099] Step 2.4, the dried waste white cardboard fibers in step 2.3 were crushed in a crusher at a speed of 29000r / min for 10s, obtaining refined fibers, which were packaged using a sealed bag.

[0100] Step 3, a wood pulp fiber / polylactic acid composite material was prepared;

[0101] Step 3.1, the fibers obtained in step 2.4 were added to N,N-dimethylformamide, and an ultrasonic cell crusher with a power of 900W was used to ultrasonically disperse the fibers at a power of 35% for 5min, obtaining a waste white cardboard fiber dispersion;

[0102] Step 3.2, polylactic acid was added to the waste white cardboard fiber dispersion, and heated and stirred in a magnetic stirrer at a water bath temperature of 70℃ and a stirring speed of 500rpm for 3h, obtaining a wood pulp fiber / polylactic acid composite solution;

[0103] Step 4, preparation of wood fiber modified polylactic acid coated paper;

[0104] Step 4.1, cut the A4 paper into 80mm x 80mm squares;

[0105] Step 4.2, pour the wood fiber / polylactic acid composite solution prepared in step 3.2 into a 100mm diameter culture dish;

[0106] Step 4.3, immerse the square A4 paper cut in step 4.1 in the wood fiber / polylactic acid composite solution in the culture dish in step 4.2 for 15s;

[0107] Step 4.4, place the A4 paper coated with the wood fiber / polylactic acid composite solution prepared in step 4.3 in a 95℃ vacuum drying oven for 1.8h to obtain wood fiber modified polylactic acid coated paper.

[0108] Example 4

[0109] The method for preparing wood fiber modified polylactic acid coated paper comprises the following steps:

[0110] Step 1, weigh the following components by weight parts: 0.27% broadleaf wood pulp board, 87.54% N,N-dimethylformamide, 2.81% A4 paper, and 9.38% polylactic acid, and the sum of the weight percentages of the above components is 100%.

[0111] Step 2, pretreatment of the broadleaf wood pulp board;

[0112] Step 2.1, crush the weighed broadleaf wood pulp board into 17mm x 6mm fragments, soak in deionized water for 45min, and the mass ratio of the wood pulp board to deionized water is 1:30;

[0113] Step 2.2, place the soaked broadleaf wood pulp board in step 2.1 into a paper pulp disintegrator, and perform beating and disintegration at a speed of 9000r / min to obtain broadleaf wood fiber;

[0114] Step 2.3, dry the broadleaf wood fiber obtained in step 2.2 in a 75℃ electric heating air drying oven for 21h;

[0115] Step 2.4, crush the dried broadleaf wood fiber in step 2.3 in a crusher at a speed of 28000r / min for 15s to obtain refined wood fiber, and seal it in a sealed bag for use.

[0116] Step 3, preparation of wood fiber / polylactic acid composite material;

[0117] Step 3.1, the fiber obtained in step 2.4 was added into N,N-dimethylformamide, and a fiber dispersion solution of broadleaf wood pulp was obtained by ultrasonic dispersion for 4 min at a power of 900 W and a power of 37% using an ultrasonic cell crusher;

[0118] Step 3.2, the polylactic acid was added into the fiber dispersion solution of broadleaf wood pulp, and a wood pulp fiber / polylactic acid composite solution was prepared by heating and stirring at a water bath temperature of 75°C and a stirring speed of 450 rpm for 2.5 h using a magnetic stirrer;

[0119] Step 4, preparation of wood pulp fiber modified polylactic acid coated paper;

[0120] Step 4.1, the A4 paper was cut into a square of 80 mm x 80 mm;

[0121] Step 4.2, the wood pulp fiber / polylactic acid composite solution prepared in step 3.2 was poured into a culture dish with a diameter of 100 mm;

[0122] Step 4.3, the square A4 paper cut in step 4.1 was placed in the culture dish containing the wood pulp fiber / polylactic acid composite solution in step 4.2 for 25 s of immersion coating;

[0123] Step 4.4, the A4 paper coated based on the wood pulp fiber / polylactic acid composite solution prepared in step 4.3 was placed in a vacuum drying oven at 90°C for 2 h to obtain wood pulp fiber modified polylactic acid coated paper.

[0124] Example 5

[0125] The method for preparing wood pulp fiber modified polylactic acid coated paper comprises the following steps:

[0126] Step 1, the following components were weighed according to the weight parts: 0.55% coniferous wood pulp board, 87.29% N,N-dimethylformamide, 2.81% A4 paper, and 9.35% polylactic acid, and the sum of the weight percentages of the above components is 100%.

[0127] Step 2, the coniferous wood pulp board was pretreated;

[0128] Step 2.1, the weighed coniferous wood pulp board was crushed into fragments of 17 mm x 6 mm and soaked in deionized water for 45 min, and the mass ratio of the wood pulp board to the deionized water was 1:30;

[0129] Step 2.2, the soaked coniferous wood pulp board in step 2.1 was placed in a paper pulp disintegrator and disintegrated at a speed of 10000 r / min to obtain coniferous wood pulp fibers;

[0130] Step 2.3, the needle-pine pulp fibers obtained in step 2.2 were dried in an electric heating drying oven at 80℃ for 18h;

[0131] Step 2.4, the dried needle-pine pulp fibers obtained in step 2.3 were crushed in a pulverizer at a rotating speed of 29000r / min for 20s to obtain refined wood pulp fibers, which were packaged in a sealed bag for later use.

[0132] Step 3, preparation of wood pulp fiber / polylactic acid composite material;

[0133] Step 3.1, the fibers obtained in step 2.4 were added into N,N-dimethylformamide, and an ultrasonic cell pulverizer with a power of 900W was used to ultrasonically disperse the fibers at a power of 37% for 4min to obtain a needle-pine pulp fiber dispersion;

[0134] Step 3.2, polylactic acid was added into the needle-pine pulp fiber dispersion, and a magnetic stirrer was used to heat and stir at a water bath temperature of 70℃ and a rotating speed of 500rpm for 3h to obtain a wood pulp fiber / polylactic acid composite solution;

[0135] Step 4, preparation of wood pulp fiber modified polylactic acid coated paper;

[0136] Step 4.1, an A4 paper was cut into a square with a side length of 80mm;

[0137] Step 4.2, the wood pulp fiber / polylactic acid composite solution prepared in step 3.2 was poured into a culture dish with a diameter of 100mm;

[0138] Step 4.3, the square A4 paper cut in step 4.1 was immersed and coated in the culture dish containing the wood pulp fiber / polylactic acid composite solution in step 4.2 for 30s;

[0139] Step 4.4, the A4 paper coated based on the wood pulp fiber / polylactic acid composite solution prepared in step 4.3 was dried in a vacuum drying oven at 90℃ for 2h to obtain a wood pulp fiber modified polylactic acid coated paper.

[0140] The cross-sectional morphology of the wood pulp fiber modified polylactic acid coated paper prepared in Example 4 was observed using a field emission scanning electron microscope (SEM); the hydrophilic / hydrophobic property and moisture resistance of the A4 paper, the polylactic acid coated paper, and the wood pulp fiber modified polylactic acid coated papers prepared in Examples 4 and 5 were detected using a contact angle measuring instrument and a water vapor transmission rate test system; the mechanical properties of the A4 paper, the polylactic acid coated paper, and the wood pulp fiber modified polylactic acid coated papers prepared in Examples 2, 3, 4, and 5 were detected using a universal testing machine; and the folding resistance of the A4 paper, the polylactic acid coated paper, and the wood pulp fiber modified polylactic acid coated papers prepared in Examples 1 and 4 was detected by folding test using a computer-controlled folding resistance tester.

[0141] like Figure 1 The SEM images show that Example 4 successfully synthesized a coated paper with a layered self-assembled sandwich structure, which consists of a three-layer structure of wood pulp fiber modified polylactic acid / A4 paper / wood pulp fiber modified polylactic acid. Figure 2 The experiment demonstrated the preparation of polylactic acid (PLA) coated paper (PLA / A4 coated paper) by impregnating and coating A4 paper with a pure polylactic acid solution. The hydrophilicity of this coated paper was reduced to some extent compared to A4 paper, which may be closely related to the strong hydrophobicity of polylactic acid itself. However, this modification did not achieve hydrophobic modification of the A4 paper. In contrast, wood pulp fiber modified PLA coated paper significantly reduced the hydrophilicity of A4 paper. In particular, the wood pulp fiber modified PLA coated paper prepared in Example 4 achieved a transformation of A4 paper from hydrophilic to hydrophobic (contact angle of 95°). Figure 3 The results show that PLA / A4 coated paper, prepared by impregnating and coating A4 paper with a pure PLA solution, exhibits a 94% higher moisture barrier than A4 paper. This indicates that the PLA impregnation coating effectively covers most of the loose, porous structure on the A4 paper surface, hindering the permeation of small-molecule water vapor. Furthermore, coated paper prepared by impregnating and coating A4 paper with a wood pulp fiber-modified PLA solution shows even higher moisture barrier properties, exceeding those of A4 paper by 98%. This demonstrates that this layered self-assembled sandwich structure effectively blocks the permeation of small-molecule water vapor. Additionally, the addition of fibers to the PLA matrix, acting as a barrier, extends the tortuous path of small-molecule water vapor permeation, thereby improving the barrier properties of the A4 paper. Figure 4 The results show that coated paper prepared by impregnating and coating A4 paper with polylactic acid solution modified with wood pulp fibers has certain improvements in mechanical properties compared with A4 paper. In particular, the coated paper prepared in Examples 3 and 4 has improved tensile strength by 23% and elongation at break by 114% respectively. Figure 5 The results show that impregnating or coating A4 paper with pure polylactic acid or polylactic acid solution modified with wood pulp fiber can significantly improve the folding endurance of A4 paper. Specifically, the folding endurance of coated paper (PLA / A4 coated paper) prepared by impregnation and coating with pure polylactic acid solution is improved by 120%, while the folding endurance of coated paper prepared by impregnation and coating with polylactic acid solution modified with wood pulp fiber is improved by 226%. Figure 4 , 5 Comprehensive analysis shows that polylactic acid modified with wood pulp fiber can improve the tensile strength of A4 paper and give it a certain degree of toughness, which is closely related to the mechanical properties of wood pulp fiber and polylactic acid itself.

[0142] The method of the application synthesizes a novel layer-by-layer assembled sandwich structure functional paper through the simple preparation process of physical blending method and dip coating method, solves the problems of poor hydrophobicity and barrier property and poor mechanical property of the existing paper, provides a path for producing functional paper, and lays a certain theoretical research foundation and practical experience for expanding the application range of paper.

Claims

1. A method for producing a wood pulp fiber-modified polylactic acid coated paper, characterized by, The method comprises the following steps: Step 1, the following components are weighed respectively according to parts by weight: 0.06%~0.55% wood pulp board, 87.29%~87.72% N,N-dimethylformamide, 2.81%~2.82% A4 paper, 9.35%~9.4% polylactic acid, and the sum of the weight percentages of the above components is 100%; In step 1, the wood pulp board is waste white paper, broadleaf wood pulp board or coniferous wood pulp board; Step 2, the wood pulp board is pretreated; Step 2 is specifically: Step 2.1, the weighed wood pulp board is crushed into 15mm×4mm~20mm×10mm fragments, and is soaked in deionized water for 30min~60min, and the mass ratio of the wood pulp board to the deionized water is 1:30; Step 2.2, the wood pulp board soaked in step 2.1 is put into a paper pulp disintegrating machine, and is beaten and disintegrated at a rotating speed of 8000r / min~10000r / min to obtain wood pulp fibers; Step 2.3, the wood pulp fibers obtained in step 2.2 are dried in an electric heating air drying oven at 70℃~80℃ for 18h~24h; Step 2.4, the dried wood pulp fibers in step 2.3 are crushed in a crusher at a rotating speed of 27000~29000r / min for 10s~30s to obtain refined wood pulp fibers, which are packaged in a sealed bag for use; Step 3, wood pulp fiber / polylactic acid composite material is prepared; Step 3 is specifically: Step 3.1, the wood pulp fibers obtained in step 2.4 are added to N,N-dimethylformamide, and an ultrasonic cell crusher with a power of 900W is used to ultrasonically disperse the wood pulp fibers for 3min~5min at a power of 35%~40% to obtain a wood pulp fiber dispersion liquid; Step 3.2, polylactic acid is added to the wood pulp fiber dispersion liquid, and heated and stirred in a magnetic stirrer at a water bath temperature of 70℃~80℃ and a rotating speed of 400rpm~500rpm for 2h~3h to prepare a wood pulp fiber / polylactic acid composite solution; Step 4, wood pulp fiber modified polylactic acid coated paper is prepared; Step 4 is specifically: Step 4.1, the A4 paper is cut into a square of 70mm×70mm~80mm×80mm; Step 4.2, the wood pulp fiber / polylactic acid composite solution prepared in step 3.2 is poured into a culture dish with a diameter of 100mm; Step 4.3, the square A4 paper cut in step 4.1 is placed in the culture dish containing the wood pulp fiber / polylactic acid composite solution in step 4.2 for impregnation and coating for 15s~30s; Step 4.4, the A4 paper coated based on the wood pulp fiber / polylactic acid composite solution prepared in step 4.3 is placed in a vacuum drying oven at 90℃~100℃ for drying for 1.5h~2h to obtain wood pulp fiber modified polylactic acid coated paper.

2. The wood pulp fiber modified polylactic acid coated paper prepared by the method according to claim 1.

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