Bio-based polyurethane adhesive for coconut husk bricks, preparation method thereof, and coconut husk bricks

Abstract

The present invention belongs to the technical field of polyurethane adhesives, and specifically relates to a bio-based polyurethane adhesive for coconut husk bricks, a preparation method thereof, and coconut husk bricks. The adhesive is composed of the following raw materials in weight percentage: 30% to 40% of bio-based polyether ester polyol, 10% to 20% of hydrophilic polyether polyol, 20% to 30% of isocyanate, 3% to 6% of silane coupling agent, 5% to 20% of plasticizer, 1% to 1.5% of antioxidant, 3% to 6% of hydrolysis resistance agent, and 0.1% to 0.2% of catalyst. The present invention has long-term water resistance, high mechanical properties, high elongation, high mechanical property retention rate after water absorption, and a certain water absorption, which can effectively extend the water supply time and has potential biodegradability. The present invention also provides a preparation method thereof and coconut husk bricks prepared with the adhesive.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane adhesives, and particularly relates to a bio-based polyurethane adhesive for coconut chaff bricks, a preparation method thereof, and coconut chaff bricks. Background Art

[0002] Coconut bran is a byproduct of coconut. It is made by crushing coconut shells. Because of its good water absorption and water retention, it can be used for the cultivation of potted plants. Coconut bran has good air permeability, which can prevent the corrosion of plant roots, promote the growth of plant roots, and protect the soil to avoid mud. Generally, coconut bran is pressed into coconut bran bricks by pressing for easy transportation and later use. When in use, put the coconut bran bricks in a container, add water, and after leaving for 15 minutes, pour out the remaining water, or add water while mixing. The coconut bran bricks expand quickly and can be completely soaked in about 5 minutes. After soaking, they can be used. Nowadays, as soilless cultivation technology becomes more and more mature, the market demand for soilless cultivation substrates is also increasing. Therefore, the technical requirements for using coconut bran as a substrate to make coconut bran bricks, which do not need to be soaked, and can be directly used for the cultivation of crops or flowers and plants are getting higher and higher. However, there are very few polyurethane adhesives for coconut husk bricks in the market. At the same time, considering that coconut husk bricks are recyclable biomass energy, bio-based adhesives should also be considered when selecting adhesives, which is conducive to energy regeneration and environmental protection. Therefore, there is a need for an adhesive suitable for coconut husk bricks that is water-absorbing and water-retaining and environmentally friendly. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a bio-based polyurethane adhesive for coconut husk bricks, which has long-term water resistance, high mechanical properties, high elongation, high mechanical property retention rate after water absorption, and has a certain water absorption, which can be slowly released to achieve the effect of water replenishment, which is more conducive to plant growth; on the premise of ensuring the shape stability and durability of the coconut husk bricks after water absorption and expansion, the water supply time can be effectively extended, and it has potential biodegradability. The present invention also provides a preparation method thereof and coconut husk bricks prepared with the adhesive.

[0004] The bio-based polyurethane adhesive for coconut husk bricks of the present invention is composed of the following raw materials in percentage by weight:

[0005] Bio-based polyetherester polyol 30%~40%,

[0006] Hydrophilic polyether polyol 10%~20%,

[0007] Isocyanate 20%~30%,

[0008] Silane coupling agent 3%~6%,

[0009] Plasticizer 5%~20%,

[0010] Antioxidant 1%~1.5%,

[0011] Hydrolysis resistant agent 3%~6%,

[0012] Catalyst 0.1%~0.2%,

[0013] Wherein, the isocyanate is toluene diisocyanate.

[0014] Preferably, the bio-based polyether ester polyol is a low-saturation, high-activity polyether ester polyol obtained by polymerizing a bio-based polyester polyol obtained by condensation of bio-based sebacic acid and bio-based 1,3-propylene glycol with ethylene oxide under the catalysis of an alkali metal catalyst KOH, and has a functionality of 2 and a number average molecular weight of 4000.

[0015] Preferably, the hydrophilic polyether polyol is ethylene oxide copolymer polyether with a functionality of 2 and a number average molecular weight of 1000, more preferably CHPEG-1000A from Changhua Chemical Technology Co., Ltd.

[0016] Preferably, the toluene diisocyanate is T-80 from BASF GmbH.

[0017] Preferably, the silane coupling agent is Z-6020, produced by Dow Corning, USA; the plasticizer is chloropalm oil methyl ester, produced by Nanjing Bermuda Biotechnology Co., Ltd.; the antioxidant is antioxidant 1010, produced by Great Lakes Chemical Company, USA; the hydrolysis resistance agent is CHINOXP-500, produced by Double Bond Chemical Co., Ltd., Taiwan, China; and the catalyst is T-12, produced by Air Products and Chemicals, Inc., USA.

[0018] The method for preparing the bio-based polyurethane adhesive for coconut husk bricks of the present invention comprises the following steps:

[0019] Add bio-based polyether ester polyol, hydrophilic polyether polyol, plasticizer and antioxidant into the reactor, start stirring, dehydrate at 110-120℃ for 3-4h, cool to 70℃ after the moisture content is less than 0.03%, add isocyanate into the reactor, heat to 85℃, keep warm for 2h, take samples to detect NCO% to 7.5-13%, cool to 50-60℃, add silane coupling agent, hydrolysis resistance agent and catalyst into the reactor, and put into barrels for later use.

[0020] The coconut husk bricks of the present invention are obtained by mixing and pressing the above-mentioned adhesive and coconut husk particles.

[0021] Preferably, the preparation method of the coconut husk brick is as follows: pour the adhesive and coconut husk particles into a container at a mass ratio of 1:2.5, stir evenly, pour into a mold and press, leave at room temperature for 7-8 hours and then open the mold to obtain the brick.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The coconut husk bricks made of the adhesive of the present invention not only do not affect the water absorption rate of the coconut husk bricks, but also have high shape stability and water resistance, which greatly improves the service life of the coconut husk bricks;

[0024] 2. The present invention adopts bio-based polyether ester polyols in combination with hydrophilic polyether polyols, wherein the bio-based polyether ester polyols have polyester polyols as the main chain segment, and the mechanical properties are greatly improved compared with conventional polyether polyols. At the same time, the grafted ethylene oxide chain segment can improve the hydrophobicity of the polyester polyols, and at the same time achieve high hydrolysis resistance, thereby improving the hydrophilicity and water resistance of the obtained polyether esters; the hydrophilic polyether polyols are embedded in the adhesive chain segment, which has good water absorption and water retention, and can extend the ability of coconut bran to supply water to plants;

[0025] 3. The invention is bio-friendly, and its preparation method is simple and easy, and is suitable for industrial production. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below in conjunction with embodiments.

[0027] Unless otherwise specified, all raw materials used in the examples are commercially available.

[0028] Among them, the bio-based polyether ester polyol is a low-saturation, high-activity polyether ester polyol obtained by polymerizing the bio-based polyester polyol obtained by the condensation of bio-based sebacic acid and bio-based 1,3-propylene glycol with ethylene oxide under the catalysis of an alkali metal catalyst KOH. It has a functionality of 2 and a number average molecular weight of 4000.

[0029] Hydrophilic polyether polyol, CHPEG-1000A, Changhua Chemical Technology Co., Ltd.;

[0030] Isocyanate, T-80, BASF SE;

[0031] Silane coupling agent, Z-6020, Dow Corning, USA;

[0032] Plasticizer, chloropalm oil methyl ester, Nanjing Bermuda Biotechnology Co., Ltd.;

[0033] Antioxidant, Antioxidant 1010, Great Lakes Chemical Company, USA;

[0034] Hydrolysis resistance agent, CHINOXP-500, Double Bond Chemical Co., Ltd., Taiwan, China;

[0035] Catalyst, T-12, Air Products & Chemicals, Inc.

[0036] Example 1

[0037] The preparation method of the adhesive is as follows:

[0038] 300g of bio-based polyether ester polyol, 200g of hydrophilic polyether polyol CHPEG-1000A, 154g of plasticizer chloropalm oil methyl ester and 15g of antioxidant 1010 were put into a reactor, and stirring was started. Dehydration was carried out at 110°C for 4h. After the moisture content was less than 0.03%, the temperature was lowered to 70°C. 250g of isocyanate T-80 was added to the reactor, and the temperature was raised to 85°C and kept warm for 2h. Samples were taken to detect NCO% to 9.76%, and the temperature was lowered to 60°C. 50g of silane coupling agent Z-6020, 30g of hydrolysis-resistant agent CHINOXP-500 and 1g of catalyst T-12 were added to the reactor, and the mixture was packed in barrels for later use.

[0039] Pour the obtained adhesive and coconut husk particles into a container at a mass ratio of 1:2.5, stir evenly and pour into a mold for pressing. After leaving at room temperature for 7 hours, open the mold to obtain a coconut husk brick sample with a side length of 10 cm.

[0040] Example 2

[0041] The preparation method of the adhesive is as follows:

[0042] 400g of bio-based polyether ester polyol, 100g of hydrophilic polyether polyol CHPEG-1000A, 198.5g of plasticizer chloropalm oil methyl ester and 10g of antioxidant 1010 were put into a reactor, and stirring was started. Dehydration was carried out at 120°C for 3h. After the moisture content was less than 0.03%, the temperature was lowered to 70°C. 200g of isocyanate T-80 was added to the reactor, and the temperature was raised to 85°C and kept warm for 2h. Samples were taken to detect NCO% to 7.97%, and the temperature was lowered to 50°C. 30g of silane coupling agent Z-6020, 60g of hydrolysis-resistant agent CHINOXP-500 and 1.5g of catalyst T-12 were added to the reactor, and the mixture was packed in barrels for later use.

[0043] Pour the obtained adhesive and coconut husk particles into a container at a mass ratio of 1:2.5, stir evenly and pour into a mold for pressing. After leaving at room temperature for 7 hours, open the mold to obtain a coconut husk brick sample.

[0044] Example 3

[0045] The preparation method of the adhesive is as follows:

[0046] 366g of bio-based polyether ester polyol, 160g of hydrophilic polyether polyol CHPEG-1000A, 50g of plasticizer chloropalm oil methyl ester and 12g of antioxidant 1010 were put into the reactor, and stirring was started. Dehydration was carried out at 110°C for 3h. After the moisture content was less than 0.03%, the temperature was lowered to 70°C. 300g of isocyanate T-80 was added to the reactor, and the temperature was raised to 85°C and kept warm for 2h. Samples were taken to detect NCO% to 12.37%, and the temperature was lowered to 60°C. 60g of silane coupling agent Z-6020, 50g of hydrolysis-resistant agent CHINOXP-500 and 2g of catalyst T-12 were added to the reactor, and the mixture was packed in barrels for later use.

[0047] Pour the obtained adhesive and coconut husk particles into a container at a mass ratio of 1:2.5, stir evenly and pour into a mold for pressing. After leaving at room temperature for 8 hours, open the mold to obtain a coconut husk brick sample with a side length of 10 cm.

[0048] Comparative Example 1

[0049] The difference between Comparative Example 1 and Example 3 is that all the bio-based polyether ester polyols in the components are replaced with polyether polyol DL-4000 of the same mass.

[0050] Comparative Example 2

[0051] The difference between Comparative Example 2 and Example 3 is that all CHPEG-1000A in the components is replaced with polyether polyol DL-1000 of the same mass.

[0052] Comparative Example 3

[0053] Compared with Example 3, the only difference in Comparative Example 3 is that all T-80 in the components are replaced with MDI-50 of the same substance weight.

[0054] Comparative Example 4

[0055] Compared with Example 3, the only difference in Comparative Example 4 is that all T-80 in the components is replaced with M20S of the same material weight.

[0056] Performance Testing

[0057] The adhesives and coconut husk brick samples obtained in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests, and the results are shown in Table 1 below. The mechanical properties were tested using 2 mm adhesive samples as standard samples, and the volume change rate was tested using coconut husk bricks as standard samples. The hydrolysis test conditions were as follows: the adhesive samples were immersed in water at 80°C and pH 13 for hydrolysis, and the changes in mechanical properties before and after hydrolysis for 7 days were compared.

[0058] Table 1 Performance test table of Examples 1-3 and Comparative Examples 1-4

[0059]

[0060] As can be seen from Table 1, compared with Comparative Examples 1 and 2, the use of bio-based polyether ester polyol and hydrophilic polyether polyol in Example 3 significantly increases the dimensional stability and water retention rate, and the volume change rate after water absorption is lower. Comparative Examples 3 and 4 have high tensile strength and low elongation, resulting in mismatch between elongation and tensile strength, low volume change rate, and cannot absorb 100% of their own mass of water; compared with Comparative Examples 3 and 4, the adhesive obtained by using T-80 in Example 3 has significantly better elongation, and the tensile strength and tear strength are not significantly reduced, and the overall performance is better.

Claims

1. A bio-based polyurethane adhesive for coconut husk bricks, characterized in that: It is composed of the following raw materials in percentage by weight: Bio-based polyether ester polyol 30%~40%, Hydrophilic polyether polyol 10%~20%, Isocyanate 20%~30%, Silane coupling agent 3%~6%, Plasticizer 5%~20%, Antioxidant 1%~1.5%, Hydrolysis resistant agent 3%~6%, Catalyst 0.1%~0.2%, Wherein, the isocyanate is toluene diisocyanate; Bio-based polyether ester polyol is a low-saturation, high-activity polyether ester polyol obtained by condensing bio-based sebacic acid and bio-based 1,3-propylene glycol with ethylene oxide under the catalysis of an alkali metal catalyst KOH, with a functionality of 2 and a number average molecular weight of 4000. The hydrophilic polyether polyol is ethylene oxide copolymer polyether, has a functionality of 2 and a number average molecular weight of 1000.

2. The bio-based polyurethane adhesive for coconut husk bricks according to claim 1, characterized in that: The silane coupling agent is Z-6020; the plasticizer is chloropalm oil methyl ester; the antioxidant is antioxidant 1010; the hydrolysis resistance agent is CHINOXP-500; and the catalyst is T-12.

3. A method for preparing a bio-based polyurethane adhesive for coconut husk bricks according to any one of claims 1 to 2, characterized in that: The steps include: Add bio-based polyether ester polyol, hydrophilic polyether polyol, plasticizer and antioxidant into the reactor, start stirring, dehydrate at 110-120℃ for 3-4h, cool to 70℃ after the moisture content is less than 0.03%, add isocyanate into the reactor, heat to 85℃, keep warm for 2h, take samples to detect NCO% to 7.5-13%, cool to 50-60℃, add silane coupling agent, hydrolysis resistance agent and catalyst into the reactor, and put into barrels for later use.

4. A coconut husk brick, characterized in that: The adhesive according to any one of claims 1 to 2 is mixed and pressed with coconut bran particles to obtain the product.

5. The coconut husk brick according to claim 4, characterized in that: The preparation method of the coconut husk brick is as follows: pour the adhesive and coconut husk particles into a container at a mass ratio of 1:2.5, stir evenly, pour into a mold, press, place at room temperature for 7-8 hours, and then open the mold to obtain the coconut husk brick.

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