Preparation method of LWRT composite board, LWRT composite board and application of LWRT composite board

Abstract

The invention relates to the technical field of preparation of LWRT composite boards, in particular to a preparation method of an LWRT composite board, the LWRT composite board and application of the LWRT composite board. Glass fibers and polypropylene fibers are sequentially subjected to opening, dry carding, cross lapping and needling, and a composite felt material is obtained; the obtained composite felt material passes through a first heating area, the non-woven fabric and the hot melt adhesive layer simultaneously pass through a second heating area along with the composite felt material from the upper surface and the lower surface of the composite felt material, and then the LWRT composite board is obtained through thermal compounding and cold setting. By controlling the selection and proportion of the non-woven fabric, the hot melt adhesive layer, the resin fiber and the glass fiber and combining a material mixing process, a needling process, a thermal compounding process, a cold setting process and the like, the bending property, the interlayer cohesive force, the thickness uniformity and the like of the composite board are remarkably improved; therefore, many challenges of existing LWRT plates in partition plate interlayers of motor homes, passenger cars and van vehicles are overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of LWRT composite plate preparation, and in particular to a preparation method of a LWRT composite plate, a LWRT composite plate and applications thereof. Background Art

[0002] Forest resources, as one of the most valuable natural resources on the earth, not only provide habitats for countless organisms, but also are the key to maintaining the ecological balance of the earth. They are like the lungs of the earth. Through photosynthesis, they absorb carbon dioxide and release oxygen, effectively regulate the climate, maintain water and soil, and reduce or even prevent the occurrence of natural disasters such as drought, flood, wind and sand, and hail. In addition, forests have multiple functions such as purifying the air, eliminating noise, protecting the soil, and maintaining biodiversity, which are vital to human survival and development. However, with the rapid development of human society, the excessive exploitation and utilization of wood resources have led to the depletion of forest resources. Although in recent years, the global attention to forest protection has been continuously improved, and the rate of forest degradation and disappearance has slowed down, large areas of forest (nearly 200 square kilometers) are still disappearing every day, which poses a great threat to the ecological environment of the earth. In the field of RV, bus and van manufacturing, traditional partition sandwich panel materials are mostly wood-based. Although these materials have certain strength and stability, with the popularization of environmental protection concepts, the increasing shortage of wood resources, and the existence of problems such as wood mildew, the need to find wood substitutes is becoming increasingly urgent. In this context, lightweight glass fiber reinforced thermoplastic composites (Light Weight Reinforced Thermoplastic), referred to as LWRT boards, began to be used in this industry.

[0003] LWRT sheet is a kind of felt material made of short-cut glass fiber and thermoplastic short fiber, which is then compounded into a board through hot compounding and cold setting process, becoming an ideal substitute for sandwich panels for partitions of RVs, buses and vans. However, the existing LWRT sheet still has many problems in application, such as insufficient bending performance of the sheet, poor surface flatness, lack of thickness uniformity, insufficient interlayer bonding force, etc., which to some extent limits its wide application in the field of sandwich panels for partitions of RVs, buses and vans. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a preparation method of an LWRT composite board, an LWRT composite board and applications thereof. The present invention controls the selection and ratio of non-woven fabric, hot-melt adhesive layer, polypropylene fiber and glass fiber, and optimizes the mixing, needling, hot compounding and cold setting processes of the materials. The present invention effectively improves the bending performance, interlayer cohesion and thickness uniformity of the composite board and solves the problem of wood being easy to mildew, thereby providing a higher-quality and more environmentally friendly solution for the partition sandwich panels of RVs, buses and vans.

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

[0006] The present invention provides a method for preparing an LWRT composite board, wherein the LWRT composite board comprises, from top to bottom, a non-woven fabric, a hot-melt adhesive layer, a composite felt material, a hot-melt adhesive layer and a non-woven fabric, and comprises the following steps:

[0007] 1) opening, dry carding, cross-laying and needle punching the glass fiber and the polypropylene fiber in sequence to obtain a composite felt material;

[0008] The mass ratio of the glass fiber to the polypropylene fiber is 40-60:40-60;

[0009] The fiber length of the glass fiber is 50 to 130 mm, and the surface oil content is 0.15 to 0.35%;

[0010] The polypropylene fiber has a fiber length of 46-76 mm, a surface oil content of 0.35-0.55%, a crimp number of 7-12, a melt index of 22-40 g / 10 min, a melting point of 166-175° C., and a crystallization temperature of 160° C.;

[0011] The acupuncture depth is 7 to 12 mm, and the needle density is 50 to 80 needles / cm 2 ;

[0012] The mass percentage of polyethylene in the non-woven fabric is 20-25%, and the gram weight is 40-80gsm;

[0013] The hot melt adhesive layer is a polypropylene perforated adhesive film with a gram weight of 20-60gsm, a hole diameter of 0.3-1mm, and a hole spacing of 3-10mm*3-10mm;

[0014] 2) The composite felt material obtained in step 1) is passed through a first heating zone, and the non-woven fabric and the hot melt adhesive layer are simultaneously passed through a second heating zone from the upper and lower surfaces of the composite felt material, followed by thermal lamination and cold setting to obtain a LWRT composite sheet;

[0015] The temperature of the first heating zone is 185-215°C, and the fan frequency is 50-80%;

[0016] The temperature of the second heating zone is 220-230°C, and the fan frequency is 90-100%;

[0017] The cold setting conditions include: the gap between the impregnation rollers is 1.5-2.0 mm, and the cooling water recovery temperature is ≤30°C.

[0018] Preferably, the glass fiber in step 1) is chopped fiber with a diameter of 17 μm, a fiber length of 110 mm, a linear density of 2400 tex, and a surface oil content of 0.25%.

[0019] Preferably, the polypropylene fiber in step 1) is short fiber with a fiber length of 60 mm, a linear density of 9 dtex, a surface oil content of 0.45%, a crimp number of 7, a melting point of 166° C., and an OIT ≥ 20 min.

[0020] Preferably, the conditions for cross-laying in step 1) include: a width of 2600 mm, 28 layers of laying, and a single web weight of 33 g / m 2 ;

[0021] The acupuncture depth is 9 mm and the needle density is 70 needles / cm 2 ;

[0022] The feed rate of the dry carding is 800-1100 kg / h.

[0023] Preferably, the thickness of the non-woven fabric in step 1) is 0.04 mm, the breaking strength is ≥ 25 N, the dimensional shrinkage under heat is ≤ 2%, and the CV% value of gram weight is ≤ 7%;

[0024] The hot melt adhesive layer has a gram weight of 30 gsm, a pore diameter of 0.5 mm, a pore distance of 7 mm*7 mm, a thickness of 28 μm, a melting point of 145° C., and the pores are arranged in a diamond and / or square shape.

[0025] Preferably, in step 2), the temperature of the first heating zone is 205° C. and the fan frequency is 70%;

[0026] The temperature of the second heating zone is 225°C and the fan frequency is 95%;

[0027] The cold setting conditions include: the gap between the impregnation rollers is 1.7 mm, the pressure between the impregnation rollers is 20 t, the line holding gap is 2.9 mm, the line holding pressure is 10 t, the surface holding gap is 2.9 mm, and the surface holding pressure is 130 t;

[0028] The conditions of the step 2) thermal compounding include: in the second heating zone, the temperature is 225° C., the fan frequency is 95%, the gap between the hot rollers is 1.5 mm, and the pressure of the hot rollers is 3 tons.

[0029] The present invention also provides a LWRT composite board prepared by the preparation method described in the above technical solution, wherein the surface density of the LWRT composite board is 980-1080gsm and the thickness is 2.9mm. In the present invention, the thickness of the non-woven fabric in the LWRT composite board is 0.04mm, the thickness of the hot melt adhesive layer is 0.03mm, the thickness of the composite felt material is 2.76mm, the thickness of the hot melt adhesive layer is 0.04mm, and the thickness of the non-woven fabric is 0.03mm.

[0030] The present invention also provides the use of the LWRT composite board material described in the above technical solution in improving the mechanical properties of the board material, wherein the mechanical properties include one or more of bending performance, interlayer cohesion, air permeability and interface bonding strength.

[0031] The present invention also provides the use of the LWRT composite board described in the above technical solution in improving the mildew resistance of the board.

[0032] The present invention also provides the use of the LWRT composite plate material described in the above technical solution in improving the thickness uniformity of the plate material.

[0033] The present invention optimizes the characteristic morphology of glass fiber and polypropylene fiber, feeds the materials in a specific proportion, and forms a composite felt material through unpacking, combing, laying nets, and needle-punching consolidation. Then, the composite felt material is pressed into a board through a continuous compounding process with a preferred hot-melt adhesive layer and a non-woven fabric layer. The glass fiber and the polypropylene fiber not only have tangled points caused by needle-punching, but also have the wrapping of the glass fiber by the polypropylene fiber after melting and the secondary consolidation of the molten polypropylene fiber at the tangled points. Furthermore, with the preferred needle-punching process, a large number of glass fibers will have their original two-dimensional planar distribution transformed into a three-dimensional distribution form. Therefore, this LWRT composite board material used in the sandwich panels of RVs, buses, and van partitions has the characteristics of high bending performance, high cohesion between high layers, excellent thickness uniformity, no mildew, and high air permeability.

[0034] The present invention optimizes the composition ratio of the non-woven fabric, and controls the mass ratio of the low-melting-point fiber component to 20±5%, so that the hot-rolled non-woven fabric can ensure a breaking strength of ≥25N, and at the same time ensure the air permeability and plush feeling of the non-woven fabric, and can provide higher interface bonding strength when preparing RV, bus, and van partitions.

[0035] Beneficial effects of the present invention:

[0036] 1. High bending performance: The present invention optimizes the characteristic forms of glass fiber and polypropylene fiber, feeds them in a specific proportion, and makes a composite felt material through unpacking, combing, laying nets, and needle punching consolidation. Then, the composite felt material is pressed into a board through a continuous compounding process with the preferred hot melt adhesive layer and non-woven fabric layer. Under the combined action of two high-temperature ovens at 185℃-215℃ and 220℃-230℃, 3t high-pressure hot rollers and 20t high-pressure impregnation rollers, the wrapping of the glass fiber by the melted polypropylene fiber and the secondary consolidation of the molten polypropylene fiber at the tangle point make the composite board after cold pressing and shaping have higher bending performance.

[0037] 2. Cohesion between high layers: The preferred needling process will transform a large amount of glass fibers from the original two-dimensional distribution to a three-dimensional distribution form, and at the same time, the glass fibers and polypropylene fibers have many entanglements caused by needling. During the board making stage, the composite felt material passes through two heating zones, so that the polypropylene fibers are fully melted, so that the glass fibers and polypropylene fibers not only have entanglements caused by needling, but also have the wrapping of the glass fibers by the melted polypropylene fibers and the secondary consolidation of the molten polypropylene fibers at the entanglements. Therefore, the LWRT board of the present invention has cohesion between high layers.

[0038] 3. Excellent thickness uniformity: The composite board material of the present invention is prepared by a continuous compounding process including hot compounding, cold setting and cutting. During the cold setting process, the composite board material is cold set by a double layer of 10t line pressure holding and 130t surface pressure holding. Furthermore, the crystallization temperature of the polypropylene fiber is controlled at 100-120°C, and the low cooling water recovery temperature is ensured to be ≤30°C, so that the core layer of the composite board material can also achieve complete cooling and setting of the polypropylene fiber. Finally, the thickness tolerance range of the board material is controlled at ±0.1mm, achieving excellent thickness uniformity.

[0039] 4. Mildew resistance: The composite board of the present invention is made of high molecular materials such as polyolefins and polyesters and inorganic materials such as glass fibers, and does not contain any materials that are prone to mildew. Therefore, the risk of mildew during use of natural materials such as wood and bamboo can be eliminated.

[0040] 5. High air permeability: The present invention strictly controls the proportion of low-melting-point components in the non-woven fabric to 20±5%, and its melting point is between 110℃ and 140℃. Furthermore, the hot-melt adhesive layer described in the present invention is in the form of a perforated film. The perforated film is characterized in that the pore size is 0.3-1mm and the pore spacing is 3-10mm*3-10mm. After the continuous composite process passes through the second heating zone and then undergoes cold setting, the low-melting-point components in the non-woven fabric and the hot-melt adhesive layer will be completely plasticized and reshaped, and countless non-continuous and irregular tiny holes will be formed on the surface of the board, giving the board air permeability. By controlling the selection of non-woven fabrics, adhesive films and the bulk density of the board, the specific fluid resistance of the composite board can be controlled within the range of 2449.8-11704.6Pa*s / m.

[0041] 6. High interfacial bonding strength: The present invention optimizes the composition ratio of the non-woven fabric, and controls the mass ratio of the low-melting-point fiber component to 20±5%. While ensuring that the breaking strength of the hot-rolled non-woven fabric is ≥25N, the air permeability and plush feeling of the non-woven fabric are also ensured. The plush feeling can improve the adsorption capacity of the board to the glue, and the appropriate air permeability can make more glue stay at the bonding interface while allowing part of the glue to penetrate into the board. Thus, when preparing the partitions of RVs, buses, and vans, higher interfacial bonding strength is obtained. DETAILED DESCRIPTION

[0042] The present invention provides a method for preparing an LWRT composite board, wherein the LWRT composite board comprises, from top to bottom, a non-woven fabric, a hot-melt adhesive layer, a composite felt material, a hot-melt adhesive layer and a non-woven fabric, and comprises the following steps:

[0043] 1) opening, dry carding, cross-laying and needle punching the glass fiber and the polypropylene fiber in sequence to obtain a composite felt material;

[0044] The mass ratio of the glass fiber to the polypropylene fiber is 40-60:40-60;

[0045] The fiber length of the glass fiber is 50 to 130 mm, and the surface oil content is 0.15 to 0.35%;

[0046] The polypropylene fiber has a fiber length of 46-76 mm, a surface oil content of 0.35-0.55%, a crimp number of 7-12, a melt index of 22-40 g / 10 min, a melting point of 166-175° C., and a crystallization temperature of 160° C.;

[0047] The acupuncture depth is 7 to 12 mm, and the needle density is 50 to 80 needles / cm 2 ;

[0048] The mass percentage of polyethylene in the non-woven fabric is 20-25%, and the gram weight is 40-80gsm;

[0049] The hot melt adhesive layer is a polypropylene perforated adhesive film with a gram weight of 20-60gsm, a hole diameter of 0.3-1mm, and a hole spacing of 3-10mm*3-10mm;

[0050] 2) The composite felt material obtained in step 1) is passed through a first heating zone, and the non-woven fabric and the hot melt adhesive layer are simultaneously passed through a second heating zone from the upper and lower surfaces of the composite felt material, followed by thermal lamination and cold setting to obtain a LWRT composite sheet;

[0051] The temperature of the first heating zone is 185-215°C, and the fan frequency is 50-80%;

[0052] The temperature of the second heating zone is 220-230°C, and the fan frequency is 90-100%;

[0053] The cold setting conditions include: the gap between the impregnation rollers is 1.5-2.0 mm, and the cooling water recovery temperature is ≤30°C.

[0054] In the present invention, the glass fiber is preferably a chopped fiber with a diameter of 17μm, a fiber length of 110mm, a linear density of 2400tex, and a surface oil content of 0.25%. In the present invention, the polypropylene fiber is preferably a short fiber with a fiber length of 60mm, a linear density of 9dtex, a surface oil content of 0.45%, a crimp number of 7, a melting point of 166°C, and OIT≥20min. The present invention does not specifically limit the sources of the glass fiber and polypropylene fiber, and conventional commercially available products can be used. In the present invention, the thickness of the non-woven fabric is 0.04mm, the breaking strength is ≥25N, the dimensional shrinkage rate under hot state is ≤2%, and the gram weight CV% value is ≤7%. In the present invention, the non-woven fabric is preferably a short fiber hot-rolled non-woven fabric, which is made of conventional black polyester fiber and white ES fiber by conventional blending and hot rolling. In the present invention, the weight of the hot melt adhesive layer is preferably 30gsm, the pore size is 0.5mm, the pore spacing is 7mm*7mm, the thickness is 28μm, the melting point is 145°C, and the holes are arranged in a diamond and / or square shape. In the present invention, the conditions for cross-laying preferably include: the width is 2600mm, the number of layup layers is 28, and the weight of a single mesh is 33g / m 2 In the present invention, the needle depth of the acupuncture is preferably 9 mm, and the needle density is 70 needles / cm 2 In the present invention, the feed rate of the dry carding is preferably 800 to 1100 kg / h.

[0055] In the present invention, the temperature of the first heating zone is preferably 205°C, and the fan frequency is 70%. In the present invention, the temperature of the second heating zone is preferably 225°C, and the fan frequency is 95%. In the present invention, the cold setting conditions preferably include: the gap between the impregnation rollers is 1.7mm, the pressure of the impregnation rollers is 20t, the line holding gap is 2.9mm, the line holding pressure is 10t, the surface holding gap is 2.9mm, and the surface holding pressure is 130t. In the present invention, the heat compounding conditions preferably include: in the second heating zone, the temperature is 225°C, the fan frequency is 95%, the hot roller gap is 1.5mm, and the hot roller pressure is 3t.

[0056] The present invention also provides a LWRT composite sheet prepared by the preparation method described in the above technical solution, wherein the surface density of the LWRT composite sheet is 980-1080 gsm and the thickness is 2.9 mm. In the present invention, the LWRT composite sheet is composed of non-woven fabric 1 (0.04 mm), hot melt adhesive layer 2 (0.03 mm), composite felt material 3 (2.76 mm), hot melt adhesive layer 4 (0.04 mm), and non-woven fabric 5 (0.03 mm) from top to bottom.

[0057] The present invention also provides the use of the LWRT composite board material described in the above technical solution in improving the mechanical properties of the board material, wherein the mechanical properties include one or more of bending performance, interlayer cohesion, air permeability and interface bonding strength.

[0058] The present invention also provides the use of the LWRT composite plate material described in the above technical solution in improving the thickness uniformity of the plate material.

[0059] The present invention also provides the use of the LWRT composite board described in the above technical solution in improving the mildew resistance of the board.

[0060] In order to further illustrate the present invention, the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0061] Example 1

[0062] A method for preparing a LWRT composite plate comprises the following steps:

[0063] Step 1: Felt making

[0064] Glass fiber and polypropylene fiber are selected as raw materials for composite felt, wherein the glass fiber is short-cut fiber with a diameter of 17 μm, a fiber length of 110 mm, a linear density of 2400 tex, and a surface oil content of 0.25%; the polypropylene fiber is short fiber with a fiber length of 60 mm, a linear density of 9 dtex, a surface oil content of 0.45%, a crimp number of 7, a melt index of 40 g / 10 min, a melting point of 166 ° C, a crystallization temperature of 160 ° C, and OIT ≥ 20 min. The mass ratio of glass fiber to polypropylene fiber is 47:53.

[0065] The pretreated glass fiber and polypropylene fiber are dragged into the bale opener in proportion, and then sent to the mixing bin after passing through multiple opening equipment. The weighed and quantitative fibers are continuously sent to the carding machine for combing. After combing, the mixed fibers form a thin single fiber web, which is then cross-laid by the web laying machine and sent to the needling area. After needling consolidation, the composite felt material is rolled up.

[0066] The feeding rate of the cotton feeding box in the mixing area is 900kg / h. During the laying process, the width is 2600mm, the number of layers is 28, and the weight of a single net is 33g / m 2 ; Needle depth is 9mm, needle density is 70 needles / cm 2 .

[0067] The composite felt material obtained had an area density of 860 gsm and a thickness of 9 mm.

[0068] Step 2: Board making:

[0069] Non-woven fabrics 1 and 5 are selected as the same short-fiber hot-rolled non-woven fabrics, which are made of black polyester fiber and white ES fiber blended and hot-rolled, wherein the PE component accounts for 20% of the total weight of the non-woven fabric, the gram weight is 40gsm, the thickness is 0.04mm, the breaking strength is ≥25N, the dimensional shrinkage rate under hot state is ≤2%, and the gram weight CV% value is ≤7%.

[0070] The hot melt adhesive layers 2 and 4 are made of the same polypropylene perforated adhesive film. The adhesive layer has a gram weight of 30gsm, a thickness of 28μm, and a melting point of 145°C. The hole diameter is 0.5mm, the hole spacing is 7mm*7mm, and the hole arrangement is a diamond arrangement.

[0071] The composite felt material 3 prepared in step 1 first passes through the first heating zone, the continuous roll non-woven fabric 1 and the hot melt adhesive layer 2 follow the composite felt material from the upper surface into the second heating zone, the continuous roll non-woven fabric 5 and the hot melt adhesive layer 4 simultaneously follow the composite felt material from the lower surface into the second heating zone, and then through thermal bonding, cold setting and cutting, a composite board is obtained.

[0072] The process parameters of the first heating zone include: temperature of 205°C, fan frequency of 70%;

[0073] The process parameters of the second heating zone include: temperature of 225°C, fan frequency of 95%;

[0074] The process parameters of thermal lamination include: in the second heating zone, the temperature is 225°C, the fan frequency is 95%, the gap between the hot rollers is 1.5mm, and the pressure of the hot rollers is 3t;

[0075] The process parameters for cold setting include: impregnation roller gap: 1.7mm, impregnation roller pressure is 20t, line holding gap is 2.9mm, line holding pressure is 10t; surface holding gap is 2.9mm, surface holding pressure is 130t, and cooling water recovery temperature is ≤30℃.

[0076] The continuous compounding speed is 10m / min. Finally, the composite board of suitable size is obtained by online cutting. The board surface density is 1000gsm and the thickness is 2.9mm.

[0077] Embodiment 2-7

[0078] Based on the embodiment, the structure, felt making process and plate making process are modified according to Table 1.

[0079] Table 1 Test data of Examples 1-7

[0080]

[0081]

[0082] Note: MD indicates the machine production output direction, and CD indicates the direction perpendicular to the machine production output direction.

[0083] It can be seen from the test data of Examples 1, 2, and 3 that, as the longer the length of the glass fiber, the more oil content, the longer the length of the polypropylene fiber, the more oil content, and the greater the number of curls, the two components of the fiber are slightly mixed unevenly when mixed; the melting index is too small and the melting point is too high, so that some polypropylene fibers are not fully melted and wrapped in the glass fiber; the glass fiber ratio is too high, which will lead to insufficient polypropylene fibers for consolidation, and some glass fibers are not consolidated. The shorter the length of the glass fiber and the polypropylene fiber, the weaker the ability to conduct stress inside the board after the board is formed, and the less oil content of the glass fiber and the polypropylene fiber, resulting in weaker interfacial compatibility of the two components of the fiber after mixing; the polypropylene fiber ratio is too high, which will lead to insufficient glass fibers for the skeleton. Based on the above reasons, the length of the glass fiber, the oil content, the length of the polypropylene fiber, the oil content, the number of curls, the melting index, the melting point, and the mass ratio of the glass fiber and the polypropylene fiber will affect the final bending modulus and interlayer cohesion of the board. The preferred glass fiber has a length of 110 mm and an oil content of 0.25%, the polypropylene fiber has a length of 60 mm, an oil content of 0.45%, a crimp number of 7, a melt index of 40 g / 10 min, and a melting point of 166° C. The mass ratio of glass fiber to polypropylene fiber is 47:53.

[0084] From the test data of Examples 1, 4 and 5, it can be seen that the felting process is characterized by a needle depth of 9 mm and a needle density of 70 needle punches / cm 2 The needle depth is increased to 12mm; the needle density is 80 needles / cm 2 The actual fiber length is reduced after some fibers in the felt material are broken due to excessive needle punching, and the bending performance and interlayer cohesion are reduced; the felt making process is from needle depth of 9mm; needle density of 70 needle punches / cm 2 The needle depth was reduced to 7 mm and the needle density was 50 needles / cm 2 The felt material is not needle-punched properly, resulting in insufficient entanglement points between the two component fibers, and the bending performance and interlayer cohesion are reduced.

[0085] It can be seen from the test data of Examples 1, 6, and 7 that the plate-making process is reduced from the first heating zone temperature of 205°C, the fan frequency of 70%, the second heating zone temperature of 225°C, and the fan frequency of 95% to the first heating zone temperature of 185°C, the fan frequency of 50%, the second heating zone temperature of 220°C, and the fan frequency of 90%, resulting in insufficient melting of the polypropylene fiber in the felt material, and the gap between the impregnation rollers is raised from 1.7mm to 2.0mm, resulting in the polypropylene fiber melting and not moving to the tangle point in place, which ultimately leads to reduced bending performance and interlayer cohesion. The plate-making process is reduced from the first heating zone temperature of 205°C, the fan frequency of 70%, the second heating zone temperature of 225°C, and the fan frequency of 95% to the first heating zone temperature of 215°C, the fan frequency of 80%, the second heating zone temperature of 230°C, and the fan frequency of 100%, and the gap between the impregnation rollers is reduced from 1.7mm to 1.5mm, and the bending performance and interlayer cohesion of the plate are improved, but the improvement rate is slowing down.

[0086] Embodiment 8-10

[0087] Based on Example 1, the structure, felt making process and plate making process are modified according to Table 2.

[0088] Table 2 Test data of Examples 1, 8-10

[0089]

[0090] It can be seen from the test data of Examples 1 and 8 that when the cooling water temperature is increased from 30°C to 80°C, the polypropylene fibers in the core layer of the board are not completely cooled and consolidated, and the thickness uniformity of the board decreases after leaving the cold setting area. It can be seen from the test data of Comparative Examples 1 and 9 that when the crystallization temperature of the polypropylene fibers is reduced from 160°C to 110°C, the polypropylene fibers in the core layer of the board are not completely cooled and consolidated, and the thickness uniformity of the board decreases after leaving the cold setting area. It can be seen from the test data of Comparative Examples 1 and 10 that when the cooling line pressure is reduced from 10t to 7t, the cooling surface pressure is reduced from 130t to 70t, and the thickness uniformity of the board decreases.

[0091] Comparative Example 1

[0092] Commercially available 2.5mm plywood

[0093] Table 3 Test data of Example 1 and Comparative Example 1

[0094]

[0095] It can be seen from the test data of Comparative Example 1 and Example 1 that irregular mold appeared on the surface of Comparative Example 1 after being placed at 20°C for 12 days, and there was no mold or change on the surface of Example 1 after being placed at 20°C for 20 days, indicating that the patent of the present invention has good mildew resistance.

[0096] Embodiment 11

[0097] Using Example 1 as the substrate, pour 250g of two-component polyurethane glue on it, and stick it on the XPS foam within 1 minute. Apply a pressure of 0.1Mpa for 24 hours to ensure that the polyurethane glue is completely cured.

[0098] Examples 12-16

[0099] Based on Example 11, the structure, felt making process and plate making process were modified according to Table 2.

[0100] Table 4 Test data of Examples 1, 11-16

[0101]

[0102] It can be seen from the test data of Examples 11, 12, and 13 that if the non-woven fabric does not contain PE, the interlayer strength of the non-woven fabric itself will be poor, so the interface bonding strength with the XPS foam will be poor, and the damage position will appear between the non-woven fabric layers. However, if the PE content in the non-woven fabric is too high, after hot compounding and cold setting, the specific flow resistance of the substrate will increase, and the glue will have difficulty in fully wetting the material interface, resulting in reduced interface bonding strength, and the damage position will be on the surface of the non-woven fabric.

[0103] It can be seen from the test data of Examples 11 and 14 that if the grammage of the nonwoven fabric increases, the substrate specific flow resistance and the interface bonding force do not change much.

[0104] It can be seen from the test data of Examples 11, 15, and 16 that if the weight of the adhesive film is reduced, the pore size is increased, and the hole spacing is reduced, the substrate specific flow resistance will be reduced, and the glue will penetrate too much into the substrate, leaving less glue at the interface to play a bonding role, so the interfacial bonding force is reduced. If the weight of the adhesive film is increased, the pore size is reduced, and the hole spacing is increased, the substrate specific flow resistance will increase, and the glue will not fully wet the material interface, resulting in a decrease in interfacial bonding force.

[0105] The composite board material of the present invention has the advantages of high bending performance, high bonding strength between high layers, excellent thickness uniformity, mildew resistance, high air permeability and high interface bonding strength. It specifically solves the current pain points of the use of sandwich panels for partitions of RVs, buses and vans, and further improves the product performance and customer satisfaction of such products.

[0106] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a LWRT composite sheet, wherein the LWRT composite sheet comprises, from top to bottom, a non-woven fabric, a hot melt adhesive layer, a composite felt material, a hot melt adhesive layer and a non-woven fabric, characterized in that: The following steps are involved: 1) opening, dry carding, cross-laying and needle punching the glass fiber and the polypropylene fiber in sequence to obtain a composite felt material; The mass ratio of the glass fiber to the polypropylene fiber is 40-60:40-60; The fiber length of the glass fiber is 50 to 130 mm, and the surface oil content is 0.15 to 0.35%; The polypropylene fiber has a fiber length of 46-76 mm, a surface oil content of 0.35-0.55%, a crimp number of 7-12, a melt index of 22-40 g / 10 min, a melting point of 166-175° C., and a crystallization temperature of 160° C.; The acupuncture depth is 7 to 12 mm, and the needle density is 50 to 80 needles / cm 2 ; The mass percentage of polyethylene in the non-woven fabric is 20-25%, and the gram weight is 40-80gsm; The hot melt adhesive layer is a polypropylene perforated adhesive film with a gram weight of 20-60gsm, a hole diameter of 0.3-1mm, and a hole spacing of 3-10mm*3-10mm; 2) The composite felt material obtained in step 1) is passed through a first heating zone, and the non-woven fabric and the hot melt adhesive layer are simultaneously passed through a second heating zone from the upper and lower surfaces of the composite felt material, followed by thermal lamination and cold setting to obtain a LWRT composite sheet; The temperature of the first heating zone is 185-215°C, and the fan frequency is 50-80%; The temperature of the second heating zone is 220-230°C, and the fan frequency is 90-100%; The cold setting conditions include: the gap between the impregnation rollers is 1.5-2.0 mm, and the cooling water recovery temperature is ≤30°C.

2. The preparation method according to claim 1, characterized in that: The glass fiber in step 1) is chopped fiber with a diameter of 17 μm, a fiber length of 110 mm, a linear density of 2400 tex, and a surface oil content of 0.25%.

3. The preparation method according to claim 1, characterized in that: The polypropylene fiber in step 1) is short fiber with a fiber length of 60 mm, a linear density of 9 dtex, a surface oil content of 0.45%, a crimp number of 7, a melting point of 166° C., and an OIT of ≥20 min.

4. The preparation method according to claim 1, characterized in that: The conditions of the cross-laying in step 1) include: the width is 2600 mm, the number of layers is 28, and the weight of a single web is 33 g / m 2 ; The acupuncture depth is 9 mm and the needle density is 70 needles / cm 2 ; The feed rate of the dry carding is 800-1100 kg / h.

5. The preparation method according to claim 1, characterized in that: In the step 1), the thickness of the non-woven fabric is 0.04 mm, the breaking strength is ≥ 25 N, the dimensional shrinkage under heat is ≤ 2%, and the CV% value of the gram weight is ≤ 7%; The hot melt adhesive layer has a gram weight of 30 gsm, a pore diameter of 0.5 mm, a pore distance of 7 mm*7 mm, a thickness of 28 μm, a melting point of 145° C., and the pores are arranged in a diamond and / or square shape.

6. The preparation method according to claim 1, characterized in that: In step 2), the temperature of the first heating zone is 205° C. and the fan frequency is 70%; The temperature of the second heating zone is 225°C and the fan frequency is 95%; The cold setting conditions include: the gap between the impregnation rollers is 1.7 mm, the pressure between the impregnation rollers is 20 t, the line holding gap is 2.9 mm, the line holding pressure is 10 t, the surface holding gap is 2.9 mm, and the surface holding pressure is 130 t; The conditions of the step 2) thermal compounding include: in the second heating zone, the temperature is 225° C., the fan frequency is 95%, the gap between the hot rollers is 1.5 mm, and the pressure of the hot rollers is 3 tons.

7. A LWRT composite board prepared by the preparation method according to any one of claims 1 to 6, wherein the LWRT composite board has a surface density of 980 to 1080 gsm and a thickness of 2.9 mm.

8. Use of the LWRT composite sheet material according to claim 7 in improving the mechanical properties of the sheet material, wherein the mechanical properties include one or more of bending properties, interlayer cohesion, air permeability and interface bonding strength.

9. Use of the LWRT composite board material according to claim 7 in improving the mildew resistance of the board material.

10. Use of the LWRT composite plate material according to claim 7 in improving the thickness uniformity of the plate material.

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