Preparation method for low-density plant fiber-based foam material, product, and use

Abstract

Disclosed in the present invention are a preparation method for a low-density plant fiber-based foam material, a product, and a use. The preparation method comprises: step 1: fully mixing raw materials including an aqueous suspension of plant fiber bundles, a biomass adhesive, a compatilizer, a plasticizer, and a nucleating agent to obtain foam slurry; and step 2: heating and foaming the foam slurry to prepare a low-density plant fiber-based foam material. According to the preparation method disclosed in the present invention, by using the aqueous suspension of plant fiber bundles as a raw material, and by using a natural biomass adhesive, a low-density (density≤100 kg / m3) and naturally biodegradable plant fiber-based foam material can be prepared by means of physical foaming, and can be used as a packaging material; moreover, the plant fiber-based foam material also has excellent apparent performance, and particularly can be applied to the field of high-quality packaging materials having higher apparent performance requirements.

Description

A preparation method of low-density plant fiber foam material and its product and application Technical Field

[0001] The present invention relates to the technical field of foaming materials, and in particular to a preparation method of a low-density plant fiber foaming material, and a product and application thereof. Background Art

[0002] Currently, the most widely used cushioning materials in my country's high-end packaging include expanded polystyrene (EPS), ethylene-vinyl acetate copolymer (EVA), and pulp molding. EPS and EVA are petroleum-based foam materials and are inexpensive, but they are difficult to biodegrade. Once they expire, they remain in the soil for hundreds of years without being decomposed by microorganisms. With the introduction of the "plastic restriction order," EPS and EVA will gradually be replaced by biodegradable high-end packaging materials. Pulp molding, primarily made from plant fibers, is naturally degradable and can be recycled in paper recycling systems. However, due to its dense structure and high rigidity, it cannot provide effective cushioning, and its high density increases transportation costs. These factors have significantly limited the use of pulp molding in high-end packaging.

[0003] Plant fiber foam materials are made from natural plant fibers, supplemented with adhesives, plasticizers, foaming agents, and nucleating agents, and are produced through heating and foaming or freeze-drying. Plant fiber foam materials are the material that most closely matches and has the greatest potential to replace petroleum-based foam materials.

[0004] For example, Chinese patent application publication number CN 102977625A discloses a plant fiber foam packaging board, its processing technology, and mold. The board is manufactured by mixing plant fibers with additives, vacuum filtration, microwave foaming, and hot air drying. The additives are disclosed as foaming agents, film-forming agents, and adhesives. The foaming agent is a mixture of azodimethylamide and ammonium bicarbonate, the film-forming agent is polyvinyl alcohol, and the adhesive is starch. However, the polyvinyl alcohol (PVA) used in the formulation is a petroleum-based polymer, which significantly affects the natural degradation properties of the product. Furthermore, the resulting product has numerous voids on its surface (Figure 1), failing to achieve the aesthetic appeal required for premium packaging.

[0005] For example, the Chinese patent document with application publication number CN 105713409A provides a fully degradable cellulose foam material, which is obtained by mixing, extruding granulation, expanding or molding modified plant fiber, hydroxypropyl starch, polyethylene glycol succinate, nano-calcium carbonate, a composite cross-linking agent, a composite foaming agent, stearic acid and liquid paraffin. The foaming agent used is a composite foaming agent composed of diisopropyl azodicarboxylate (DIAD) and azodicarbonamide (AC). The decomposition product NH3 of this foaming agent not only pollutes the environment but also poses a safety hazard.

[0006] Another example is a Chinese patent application publication number CN102505579A, which provides a method for preparing a plant fiber cushioning material. The method uses plant fiber as the starting material and adopts a wet molding process. The method is directly prepared through the steps of adding water to disintegrate, placing in a mold, dehydrating and molding, and drying and finishing. This technical solution avoids the addition of external raw materials such as cross-linking agents and binders, but the density of the product is only 100 to 200 kg / m 3 .

[0007] For example, Chinese patent application publication number CN 108624073 A discloses a plant fiber foam material and its production method, comprising 40-50 parts of plant fiber, 10-20 parts of adhesive, 15-30 parts of surfactant, 10-20 parts of aerogel, and 0.5-2 parts of foaming agent. The adhesive is further specified to be at least one of polyurethane and resin. The foam material prepared by this technical solution has a density of 76.3 to 92.3 kg / m 3 However, the use of petroleum-based polymer materials as adhesives will still have a significant impact on the natural degradation performance of the product.

[0008] In summary, existing plant fiber foam materials all have certain defects, such as adding petroleum-based polymer materials, using chemical foaming agents that have adverse effects on the environment or safety, poor surface aesthetics, or relatively high density, so they need to be improved.

[0009] Summary of the Invention

[0010] In view of the above problems existing in the prior art, the present invention discloses a method for preparing a plant fiber foam material, which uses an aqueous suspension of plant fiber bundles as raw material and a natural biomass adhesive to prepare a low-density (density ≤ 100kg / m 3 ) and naturally degradable plant fiber foam material can be used as packaging material; the plant fiber foam material also has excellent surface performance, especially can be used in the field of high-quality packaging materials with higher requirements on surface performance.

[0011] The specific technical solutions are as follows:

[0012] A method for preparing a low-density plant fiber foam material comprises the following steps:

[0013] Step 1: fully mixing raw materials including a water suspension of plant fiber bundles, a biomass adhesive, a compatibilizer, a plasticizer, and a nucleating agent to obtain a foaming slurry;

[0014] The concentration of the aqueous suspension of the plant fiber bundle is 6 to 40 wt%;

[0015] The mass ratio of the dry weight of the plant fiber bundle to the biomass adhesive in the aqueous suspension of the plant fiber bundle is (3-19):1;

[0016] Step 2: heating and foaming the foaming slurry to prepare the low-density plant fiber foam material.

[0017] The present invention discloses a method for preparing a plant fiber foam material. The method comprises the following steps: using an aqueous suspension of plant fiber bundles as a raw material and adopting a natural biomass adhesive to prepare a low-density and naturally degradable plant fiber foam material by physical foaming; and regulating the density and apparent properties of the prepared plant fiber foam material by regulating the concentration of the aqueous suspension of plant fiber bundles and the mass ratio of the dry weight of the plant fiber bundles to the biomass adhesive in the aqueous suspension of plant fiber bundles.

[0018] The results of the experiment showed that when the concentration of the aqueous suspension of plant fiber bundles is controlled at 6-40wt%, the density of the final prepared plant fiber foam material can be guaranteed to be ≤100kg / m 3 When the concentration is too low (such as 5wt%), it may lead to an increase in density, and at the same time cause the apparent performance of the foaming material to deteriorate significantly, and a large number of depressions and holes will appear on the surface of the product.

[0019] Preferably, the concentration of the aqueous suspension of the plant fiber bundle is 25-35wt%, and the apparent performance of the plant fiber foam material prepared at this time is better, the product surface is smooth and flat, and there are no holes visible to the naked eye; further preferably, the concentration of the aqueous suspension of the plant fiber bundle is 35wt%, and the density of the plant fiber foam material prepared at this time is lower and the 50% strain compressive strength is smaller.

[0020] The experiment found that the mass ratio of the dry weight of the plant fiber bundle to the biomass adhesive in the water suspension of the plant fiber bundle will also significantly affect the density and apparent properties of the final prepared plant fiber foam material; when the mass ratio of the dry weight of the plant fiber bundle to the biomass adhesive is (3-19):1, the density of the prepared plant fiber foam material is low, less than 80kg / m 3 When the mass ratio of the two is too large (such as 20:1), the density will increase significantly, and the apparent performance of the foamed material will deteriorate significantly, resulting in a large number of depressions and holes on the surface of the product.

[0021] Preferably, the mass ratio of the dry weight of the plant fiber bundle to the biomass adhesive is (3-10):1. In this case, the prepared plant fiber foam material has a lower density, a smaller 50% strain compressive strength, and better apparent performance.

[0022] In step one:

[0023] The aqueous suspension of plant fiber bundles is obtained by using plant fiber pulp as raw material and undergoing decomposition and dehydration;

[0024] At this time, the dry weight of the plant fiber bundle is the mass of the plant fiber pulp board used.

[0025] The plant fiber pulp board is prepared from one or more of softwood pulp fibers, hardwood pulp fibers, bamboo pulp fibers, sugarcane pulp fibers, and straw pulp fibers as raw materials.

[0026] In step one:

[0027] The biomass adhesive is selected from one or more of starch, sodium alginate, soy protein, xanthan gum, carrageenan, guar gum, gelatin, and locust bean gum;

[0028] Preferably, the biomass adhesive is selected from starch, or a mixture of starch and one or more of sodium alginate, soy protein, xanthan gum, carrageenan, guar gum, gelatin, and locust bean gum;

[0029] More preferably, the biomass adhesive is selected from a mixture of starch and other types of biomass adhesives, such as a mixture of starch, xanthan gum and guar gum, such as a mixture of starch and gelatin, and the like.

[0030] Experiments have shown that, with the optimization of the types of the above-mentioned biomass adhesives, the density of the ultimately prepared plant fiber foam material can be further reduced and its surface properties can be improved.

[0031] The compatibilizer is selected from one or more of citric acid, stearic acid, magnesium stearate, calcium stearate, sodium borate, gallic acid, and erucamide;

[0032] Preferably, the compatibilizer is selected from citric acid, or a mixture of citric acid and one or more of stearic acid, magnesium stearate, calcium stearate, sodium borate, gallic acid, and erucamide.

[0033] Experiments have shown that using citric acid alone or a mixture containing citric acid as a compatibilizer can further reduce the density of the ultimately prepared plant fiber foam material.

[0034] The present invention has no special requirements for the type of plasticizer, and common types in the art can be selected, such as water, glycerin, sorbitol, ethylene glycol, formamide, urea, etc.

[0035] The present invention has no special requirements for the type of nucleating agent, and common types in the art can be selected, such as nano-silicon dioxide, talc, sodium montmorillonite, calcium carbonate, sodium chloride, etc.

[0036] In step 1, the mass ratio of the biomass adhesive, the compatibilizer, the plasticizer, and the nucleating agent is 100:(2-20):(30-80):(10-40); preferably 100:(5-15):(30-50):(20-40).

[0037] In step 2:

[0038] The heating and foaming is carried out using conventional heating equipment in the art, such as one or more of a microwave heater, a flat plate vulcanizer, and a hot air dryer;

[0039] The heating and foaming temperature is 100-210°C;

[0040] Preferably, the heating and foaming temperature is 120-210°C, specifically 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C;

[0041] More preferably, the heating and foaming temperature is 140-210° C.; the density of the plant fiber foam material prepared at this foaming temperature is lower;

[0042] More preferably, the heating and foaming temperature is 140-180°C;

[0043] The most preferred temperature is 140-160° C. The plant fiber foam material prepared at this foaming temperature has both low density and excellent surface properties.

[0044] The present invention also discloses a low-density plant fiber foam material prepared by the above method, with a density of ≤100kg / m 3 Preferably, the density is 25 to 100 kg / m 3 .

[0045] The present invention also discloses the application of the low-density plant fiber foam material in packaging materials, and in particular, the low-density plant fiber foam material can be applied to the field of high-quality packaging materials with higher requirements on appearance performance.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] The invention discloses a method for preparing a plant fiber foam material. The method uses an aqueous suspension of plant fiber bundles as a raw material, adopts a natural biomass adhesive, and prepares a low-density and naturally degradable plant fiber foam material by physical foaming. The natural biomass adhesive is used to replace petroleum-based polymer adhesives such as PVA to bond plant fibers and form a continuous phase, so that the prepared foam material can be naturally degraded. Water vapor is used for physical foaming to replace chemical foaming agents, thereby reducing the adverse effects of chemical foaming agents on the environment and products. More importantly, the density and apparent properties of the prepared plant fiber foam material can be controlled by using the above-mentioned raw material types and coordinating the concentration of the aqueous suspension of plant fiber bundles and the mass ratio of the dry weight of the plant fiber bundles to the biomass adhesive in the aqueous suspension of the plant fiber bundles, thereby preparing a low-density plant fiber foam material.

[0048] The density of the low-density plant fiber foam material prepared by the present invention is ≤100kg / m 3 , preferably ≤80kg / m 3 , more preferably ≤55kg / m 3 , further preferably ≤35kg / m 3 , the lowest can reach 25kg / m 3 At the same time, the plant fiber foam material also has excellent surface properties and can be used in the field of packaging materials, especially in the field of high-quality packaging materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG1 is a photograph of the plant fiber foam material prepared in Example 1;

[0050] FIG2 is a photograph of the plant fiber foam material prepared in Example 2;

[0051] FIG3 is a photograph of the plant fiber foam material prepared in Example 4;

[0052] FIG4 is a photograph of the plant fiber foam material prepared in Comparative Example 1;

[0053] FIG5 is a photograph of the plant fiber foam material prepared in Example 7;

[0054] FIG6 is a photograph of the plant fiber foam material prepared in Comparative Example 2. DETAILED DESCRIPTION

[0055] In order to further understand the present invention, the present invention is described in detail below with reference to the embodiments and drawings, but the present invention is not limited to these embodiments. Non-essential improvements and adjustments made by technicians in this field under the core guiding idea of ​​the present invention still fall within the scope of protection of the present invention.

[0056] With reference to GB / T 8168-2008 standard, the density and static compression performance tests were performed on the plant fiber foam materials prepared in this embodiment or the comparative example.

[0057] Example 1

[0058] Step 1: adding 6 kg of plant fiber pulp (the mass ratio of softwood fiber pulp to bamboo fiber pulp is 7:3) and 180 kg of water into a pulper, deflocculent the fibers at a speed of 30 Hz for 30 minutes, discharging and dehydrating for 10 minutes to obtain a 35 wt% aqueous suspension of plant fiber bundles;

[0059] Step 2: 35 wt% of an aqueous suspension of plant fiber bundles, 1 kg of a biomass adhesive consisting of starch, xanthan gum, and guar gum (the mass ratio of the three is 5:3:2), 0.3 kg of glycerin, 0.1 kg of a compatibilizer consisting of citric acid and calcium stearate (the mass ratio of the two is 8:2), and 0.3 kg of talc are placed in a kneader, the kneader temperature is adjusted to 85°C and the speed is 40 Hz, and kneading is performed for 70 minutes to obtain a foaming slurry;

[0060] Step 3: Divide the foaming slurry into small pieces of about 1.3 kg using a quantitative system, and use a conveyor belt to transport the foaming slurry into the mold;

[0061] Step 4: continuously convey the filled foaming mold to a microwave heater, heat it to 140° C. for foaming, remove the mold from the microwave heater outlet, demould, and punch to obtain a low-density plant fiber foam material.

[0062] The density and 50% strain compressive strength of the plant fiber foam material prepared in this example are listed in Table 1 below.

[0063] FIG1 is a photograph of the plant fiber foam material prepared in the example. The surface of the product is smooth and flat, with no holes visible to the naked eye.

[0064] Example 2

[0065] The preparation process is basically the same as that in Example 1, except that:

[0066] The dehydration in step 1 was performed for 2 minutes, thereby obtaining a 6 wt % aqueous suspension of plant fiber bundles.

[0067] The density and 50% strain compressive strength of the plant fiber foam material prepared in this example are listed in Table 1 below.

[0068] FIG2 is a photograph of the plant fiber foam material prepared in this embodiment. Upon observation, the surface flatness is good, but there are a large number of holes visible to the naked eye on the surface.

[0069] Example 3

[0070] The preparation process is basically the same as that in Example 1, except that:

[0071] The dehydration in step 1 was performed for 8 minutes, thereby obtaining a 25 wt% aqueous suspension of plant fiber bundles.

[0072] The density and 50% strain compressive strength of the plant fiber foam material prepared in this example are listed in Table 1 below.

[0073] Upon observation, the surface of the plant fiber foam material prepared in this embodiment was smooth and flat, without visible holes, and its apparent performance was similar to that in Example 1.

[0074] Example 4

[0075] The preparation process is basically the same as that in Example 1, except that:

[0076] The dehydration in step 1 was performed for 15 minutes, thereby obtaining a 40 wt% aqueous suspension of plant fiber bundles.

[0077] The density and 50% strain compressive strength of the plant fiber foam material prepared in this example are listed in Table 1 below.

[0078] FIG3 is a photograph of the plant fiber foam material prepared in this embodiment. The surface flatness of the material is good, but there are holes visible to the naked eye on the surface.

[0079] Comparative Example 1

[0080] The preparation process is basically the same as that in Example 1, except that:

[0081] The dehydration in step 1 was performed for 1 minute, thereby obtaining a 5 wt% aqueous suspension of the plant fiber bundles.

[0082] The density and 50% strain compressive strength of the plant fiber foam material prepared in this comparative example are listed in Table 1 below.

[0083] FIG4 is a photograph of the plant fiber foam material prepared in this comparative example, which has poor surface flatness and contains a large number of depressions and holes visible to the naked eye.

[0084] Example 5

[0085] The preparation process is basically the same as that in Example 1, except that:

[0086] The mass of the biomass adhesive in step 2 is replaced with 2 kg. At this time, the mass ratio of the dry weight of the plant fiber pulp board added in step 1 to the biomass adhesive is replaced with 3:1.

[0087] The density and 50% strain compressive strength of the plant fiber foam material prepared in this example are listed in Table 1 below.

[0088] Upon observation, the product prepared in this embodiment has a smooth and flat surface, with no holes visible to the naked eye, which is similar to that of Example 1.

[0089] Example 6

[0090] The preparation process is basically the same as that in Example 1, except that:

[0091] The mass of the biomass adhesive in step 2 is replaced with 0.6 kg. At this time, the mass ratio of the dry weight of the plant fiber pulp board added in step 1 to the biomass adhesive is replaced with 10:1.

[0092] The density and 50% strain compressive strength of the plant fiber foam material prepared in this example are listed in Table 1 below.

[0093] Upon observation, the product prepared in this embodiment has a smooth and flat surface with no holes visible to the naked eye, which is similar to that of Example 1.

[0094] Example 7

[0095] The preparation process is basically the same as that in Example 1, except that:

[0096] The mass of the biomass adhesive in step 2 is replaced with 0.32 kg. At this time, the mass ratio of the dry weight of the plant fiber pulp board added in step 1 to the biomass adhesive is replaced with 19:1.

[0097] The density and 50% strain compressive strength of the plant fiber foam material prepared in this example are listed in Table 1 below.

[0098] FIG5 is a photograph of the plant fiber foam material prepared in this example. The surface smoothness of the material is good, but a large number of holes visible to the naked eye are present.

[0099] Comparative Example 2

[0100] The preparation process is basically the same as that in Example 1, except that:

[0101] The mass of the biomass adhesive in step 2 is replaced with 0.3 kg. At this time, the mass ratio of the dry weight of the plant fiber pulp board added in step 1 to the biomass adhesive is replaced with 20:1.

[0102] The density and 50% strain compressive strength of the plant fiber foam material prepared in this example are listed in Table 1 below.

[0103] FIG6 is a photograph of the plant fiber foam material prepared in this comparative example, which has poor surface flatness and contains a large number of depressions and holes visible to the naked eye.

[0104] Examples 8 to 11

[0105] The preparation process is basically the same as that in Example 1, except that:

[0106] The heating and foaming temperatures in step 4 were replaced with 120°C, 160°C, 190°C, and 210°C in sequence.

[0107] Observation showed that when the heating and foaming temperature was 120°C, the surface flatness of the prepared product was good, but there were a few holes visible to the naked eye.

[0108] When the heating foaming temperature is 160°C, the surface morphology of the prepared product is similar to that in Example 1;

[0109] When the heating foaming temperature is 190° C. to 210° C., the surface morphology of the prepared product is similar to that in Example 1, but yellowing occurs.

[0110] Example 12

[0111] The preparation process is basically the same as that in Example 1, except that in step (2):

[0112] Starch alone was used as the biomass adhesive, and the compatibilizer was replaced by citric acid, sodium borate, and magnesium stearate (the mass ratio of the three was 2:2:1); the amounts of the biomass adhesive and the compatibilizer remained unchanged.

[0113] The density and 50% strain compressive strength of the plant fiber foam material prepared in this example are listed in Table 1 below.

[0114] Observation shows that the surface of the product prepared in this embodiment is relatively smooth, but there are a small number of holes visible to the naked eye.

[0115] Example 13

[0116] The preparation process is basically the same as that in Example 1, except that in step (2):

[0117] The biomass adhesive was replaced with one composed of starch and gelatin (the mass ratio of the two was 3:2), and the compatibilizer was replaced with one composed of sodium borate and erucamide (the mass ratio of the two was 7:3).

[0118] The density and 50% strain compressive strength of the plant fiber foam material prepared in this example are listed in Table 1 below.

[0119] Upon observation, the product prepared in Example 13 had a smooth and flat surface with no visible holes, which was similar to that in Example 1.

[0120] Table 1

[0121] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. The above description of the present invention using specific examples is only used to help understand the present invention and is not intended to limit the present invention. Those skilled in the art of the present invention can also make several simple deductions, modifications, substitutions or combinations based on the concept of the present invention. These deductions, modifications, substitutions or combinations also fall within the scope of the claims of the present invention.

Claims

1. A preparation method of a low-density plant fiber foaming material, characterized in that, It includes the following steps: Step 1: Sufficiently mix raw materials including an aqueous suspension of plant fiber bundles, a biomass adhesive, a compatibilizer, a plasticizer, and a nucleating agent to obtain a foaming slurry; The concentration of the aqueous suspension of the plant fiber bundles is 6 - 40 wt%; The mass ratio of the dry weight of the plant fiber bundles in the aqueous suspension of the plant fiber bundles to the mass of the biomass adhesive is (3 - 19):1; Step 2: Heat and foam the foaming slurry to prepare the low-density plant fiber foamed material.

2. The preparation method of the low-density plant fiber foaming material according to claim 1, characterized in that, In Step 1: The aqueous suspension of the plant fiber bundles is obtained by using a plant fiber pulp board as a raw material and subjecting it to beating and dehydration; The plant fiber pulp board is prepared from one or more of softwood pulp fibers, hardwood pulp fibers, bamboo pulp fibers, sugarcane pulp fibers, and rice straw pulp fibers as raw materials.

3. The preparation method of the low-density plant fiber foaming material according to claim 1, characterized in that, In Step 1: The biomass adhesive is selected from one or more of starch, sodium alginate, soy protein, xanthan gum, carrageenan, guar gum, gelatin, and locust bean gum; The compatibilizer is selected from one or more of citric acid, stearic acid, magnesium stearate, calcium stearate, sodium borate, gallnut acid, and erucamide.

4. The preparation method of the low-density plant fiber foaming material according to claim 1, characterized in that, In Step 1: The mass ratio of the biomass adhesive, the compatibilizer, the plasticizer, and the nucleating agent is 100:(2 - 20):(30 - 80):(10 - 40); The plasticizer is selected from one or more of water, glycerol, sorbitol, ethylene glycol, formamide, and urea; The nucleating agent is selected from one or more of nano-silica, talc powder, sodium-based montmorillonite, calcium carbonate, and sodium chloride.

5. The preparation method of the low-density plant fiber foaming material according to claim 1, characterized in that, In Step 2, the temperature of the heat foaming is 100 - 210 °C.

6. The preparation method of the low-density plant fiber foamed material according to any one of claims 1 - 5, characterized in that: The biomass adhesive is selected from starch, or a mixture composed of starch and one or more of sodium alginate, soy protein, xanthan gum, carrageenan, guar gum, gelatin, and locust bean gum; The compatibilizer is selected from citric acid, or a mixture composed of citric acid and one or more of stearic acid, magnesium stearate, calcium stearate, sodium borate, gallnut acid, and erucamide.

7. The preparation method of the low-density plant fiber foaming material according to claim 6, characterized in that, The mass ratio of the dry weight of the plant fiber bundles in the aqueous suspension of the plant fiber bundles to the mass of the biomass adhesive is (3 - 10):

1.

8. The preparation method of the low-density plant fiber foaming material according to claim 7, characterized in that, The temperature of the heat foaming is 120 - 210 °C.

9. A low-density plant fiber foamed material prepared by the method according to any one of claims 1 to 8, characterized in that, The density of the low-density plant fiber foaming material ≤ 100 kg / m 3 .

10. The application of the low-density plant fiber foamed material according to claim 9 in packaging materials.

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