A fast-aging rigid crosslinked polyvinyl chloride foam and a method for preparing the same

Abstract

The application belongs to the technical field of foam materials, and particularly relates to a rigid cross-linked polyvinyl chloride foam material and a preparation method thereof. The cross-linked polyvinyl chloride foam material comprises 100 parts of polyvinyl chloride, 20-120 parts of isocyanate, 5-20 parts of a foaming agent, 2-30 parts of an acid anhydride and 0-1 part of a catalyst. The cross-linked polyvinyl chloride foam material solves the problem of long production cycle in the prior art, and can improve the quality of the foam.

Description

Technical Field

[0001] This invention relates to the field of polymer foam materials technology, specifically to a rapidly curing rigid cross-linked polyvinyl chloride foam material and its preparation method. Background Technology

[0002] Rigid cross-linked polyvinyl chloride foam has the advantages of low density and high strength, and is widely used in sandwich composite materials such as wind turbine blades, railway locomotives, ships and aerospace.

[0003] Several existing patents disclose the formulations and production processes of rigid cross-linked polyvinyl chloride (PVC) foam. These primarily use PVC, isocyanate, and acid anhydride as raw materials. The materials are mixed and poured into a mold, then subjected to high temperature and high pressure conditions where a foaming agent thermally decomposes to produce a microporous elastomer. Simultaneously, some isocyanate reacts with the acid anhydride to generate polyimide. The microporous elastomer is then transferred to a boiling or steam environment, where isocyanate reacts with water to generate CO2 gas for secondary foaming. This process also produces polyurea and polyamide structures. Finally, the foam is transferred to a steam environment for curing, consuming the remaining isocyanate. However, due to the slow diffusion rate of water vapor in rigid PVC foam, the curing time under current traditional processes is long, reducing production efficiency. Patent CN 112812473B provides a low thermal conductivity rigid cross-linked PVC foam material and its preparation method, which can shorten the original 15-30 day production cycle to 6 days. Patent CN 104672705 B discloses a cross-linked polyvinyl chloride (PVC) foam that can shorten the curing time to 4-6 days by adding hexahydrotriazine and carboxylate catalysts. CN 111607177A introduces 7-10 parts of trifunctional polyethylene oxide-terminated propylene oxide into the formulation to improve the strength and modulus of the foam. However, existing technologies struggle to significantly shorten the curing time while maintaining foam performance. Therefore, it is necessary to develop a method to improve the curing efficiency of cross-linked PVC foam while maintaining its performance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a rigid cross-linked polyvinyl chloride foam that can be rapidly cured and its preparation method. This invention can effectively shorten the curing time of rigid cross-linked polyvinyl chloride foam materials without causing deterioration of the mechanical properties of the material itself, and can also improve the problem of foam brittleness.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0006] On one hand, the present invention provides a rigid cross-linked polyvinyl chloride foam material comprising the following components: 100 parts of polyvinyl chloride; 20-120 parts of modified isocyanate; 5-20 parts of foaming agent; 2-30 parts of acid anhydride; and 0-1 parts of catalyst.

[0007] The modified isocyanate comprises 1%-10% by mass of isocyanate-terminated polyethylene glycol urethane and 90%-99% of one or more of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and carbodiimide modified isocyanate.

[0008] The modified isocyanate is obtained by mixing 1 part by weight of polyethylene glycol with 4-100 parts, preferably 10-50 parts, of diisocyanate, such as diphenylmethane diisocyanate, at 60-90°C for 0.5-4 hours, and adding 0-95 parts of one or more of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and carbodiimide / urea ketone imide modified isocyanate and mixing them evenly.

[0009] The polyethylene glycol has a molecular weight of 200-8000 and a functionality of 2.

[0010] In this invention, the foaming agent is one or a mixture of two of azobisisobutyronitrile and azodicarbonamide.

[0011] In this invention, the acid anhydride is one or more of phthalic anhydride, maleic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and succinic anhydride, preferably methylhexahydrophthalic anhydride.

[0012] In this invention, the catalyst is one or more of sodium octanoate, potassium octanoate, potassium stearate, and calcium stearate.

[0013] On the other hand, the present invention provides a method for preparing rigid cross-linked polyvinyl chloride foam material, the method comprising the following steps: (1) mixing polyvinyl chloride, modified isocyanate, foaming agent, acid anhydride and catalyst in proportion to obtain a paste mixture; (2) transferring the above paste mixture into a mold and hot pressing it; (3) cooling, depressurizing, opening the mold and taking out the molded foam from the mold; (4) placing the above molded foam in a water bath or steam environment for secondary foaming treatment to obtain secondary foamed foam; (5) placing the above secondary foamed foam in a steam environment for curing to obtain rigid cross-linked foam.

[0014] The hot pressing is carried out in a flat vulcanizing machine. The hot pressing pressure is 15-30 MPa, the hot pressing temperature is 150-200℃, and the hot pressing time is 5-20 min.

[0015] The secondary foaming process involves a water bath or steam temperature of 70-100℃ and a time of 1-4 hours.

[0016] The curing temperature is 50-80℃, and the curing time is 5-12 days. Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) By adopting the production process provided by the present invention, while retaining the good mechanical properties of foam materials such as high strength, high toughness, high closed-cell rate and low density, the diffusion rate of water vapor in the foam can be accelerated, the foam curing time can be significantly shortened, and the production efficiency can be greatly improved.

[0018] (2) The preparation method provided by the present invention can introduce ether bonds and urethane bonds into polyvinyl chloride foam, thereby improving the toughness of the material and alleviating the brittleness problem of rigid polyvinyl chloride foam. At the same time, the structure is more uniform and the foam quality is better when the internal and external curing is complete.

[0019] (3) By adding modified isocyanate, the viscosity of the paste can be avoided, and the affinity between isocyanate and water can be effectively increased. When used with a catalyst, the curing efficiency can be greatly improved. Detailed Implementation

[0020] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0021] Raw materials and sources:

[0022]

[0023] Test method:

[0024] Compressive strength was tested using a universal tensile testing machine, following the method specified in GB / T 8813-2020.

[0025] Tensile strength and elongation at break were tested using a universal tensile testing machine, with the method referring to GB / T 9641-1988;

[0026] Shear strength was tested using a universal tensile testing machine, following the method specified in GB / T 10007-2008.

[0027] Foam density was tested using a foam density tester, referring to GB / T 6343-2009;

[0028] The foam curing time was measured using a Fourier transform infrared spectroscopy (FTIR) instrument, with the disappearance of the isocyanate characteristic peak as the curing endpoint.

[0029] Example 1:

[0030] The raw materials, by mass fraction, consist of: 100 parts polyvinyl chloride; 40 parts modified isocyanate; 5 parts blowing agent; 30 parts acid anhydride; and 0.5 parts catalyst. The modified isocyanate is composed of 1 part polyethylene glycol (molecular weight 200) and 20 parts diphenylmethane diisocyanate, reacted at 80°C for 2 hours, followed by the addition of 21 parts carbodiimide / urea-ketimide modified isocyanate. The blowing agent is a mixture of azobisisobutyronitrile and azodicarbonamide at a mass ratio of 5:1. The acid anhydride is a mixture of phthalic anhydride and hexahydrophthalic anhydride at a mass ratio of 3:1. The catalyst is a mixture of sodium octanoate and potassium octanoate at a mass ratio of 1:1.

[0031] The above-mentioned polyvinyl chloride, acid anhydride, modified isocyanate, catalyst, and heat stabilizer are mixed under vacuum to obtain a paste.

[0032] The paste is transferred to a molding machine and hot-pressed to obtain a molded bubble.

[0033] The molded foam is then subjected to secondary foaming, cross-linking, and curing in a moisture environment;

[0034] The above-mentioned cross-linked foam was cured in a water vapor environment to obtain rigid cross-linked polyvinyl chloride foam.

[0035] The molding pressure is 15MPa, the molding temperature is 150℃, the molding time is 20min, the secondary foaming temperature is 70℃, the foaming time is 4 hours, and the curing temperature is 80℃.

[0036] Example 2:

[0037] The raw materials, by mass fraction, consist of: 100 parts polyvinyl chloride; 70 parts modified isocyanate; 15 parts blowing agent; 15 parts acid anhydride; and 1 part catalyst. The modified isocyanate is obtained by reacting 1 part polyethylene glycol (molecular weight 2000) and 4 parts diphenylmethane diisocyanate at 80℃ for 2 hours, followed by the addition of 5 parts polymethylene polyphenyl polyisocyanate. The blowing agent is a mixture of azobisisobutyronitrile and azodicarbonamide in a mass ratio of 5:1. The acid anhydride is methylhexahydrophthalic anhydride, and the catalyst is potassium stearate.

[0038] The above-mentioned polyvinyl chloride, acid anhydride, modified isocyanate, catalyst, and heat stabilizer are mixed under vacuum to obtain a paste.

[0039] The paste is transferred to a molding machine and hot-pressed to obtain a molded bubble.

[0040] The molded foam is then subjected to secondary foaming, cross-linking, and curing in a moisture environment;

[0041] The above-mentioned cross-linked foam was cured in a water vapor environment to obtain rigid cross-linked polyvinyl chloride foam.

[0042] The molding pressure is 20MPa, the molding temperature is 170℃, the molding time is 15min, the secondary foaming temperature is 95℃, the foaming time is 3 hours, and the curing temperature is 70℃.

[0043] Example 3:

[0044] The raw materials, by mass fraction, consist of: 100 parts polyvinyl chloride; 120 parts modified isocyanate; 20 parts blowing agent; 2 parts acid anhydride; and 0 parts catalyst. The modified isocyanate is obtained by reacting 1 part polyethylene glycol (molecular weight 8000) with 100 parts diphenylmethane diisocyanate at 80°C for 2 hours. The blowing agent is a mixture of azobisisobutyronitrile and azodicarbonamide at a mass ratio of 5:1. The acid anhydride is a mixture of maleic anhydride and succinic anhydride at a mass ratio of 1:1.

[0045] The above-mentioned polyvinyl chloride, acid anhydride, modified isocyanate, catalyst, and heat stabilizer are mixed under vacuum to obtain a paste.

[0046] The paste is transferred to a molding machine and hot-pressed to obtain a molded bubble.

[0047] The molded foam is then subjected to secondary foaming, cross-linking, and curing in a moisture environment;

[0048] The above-mentioned cross-linked foam was cured in a water vapor environment to obtain rigid cross-linked polyvinyl chloride foam.

[0049] The molding pressure is 30MPa, the molding temperature is 200℃, the molding time is 5min, the secondary foaming temperature is 100℃, the foaming time is 1 hour, and the curing temperature is 50℃.

[0050] Example 4:

[0051] The raw materials, by mass fraction, consist of: 100 parts polyvinyl chloride; 100 parts modified isocyanate; 10 parts blowing agent; 20 parts acid anhydride; and 0.1 parts catalyst. The modified isocyanate is composed of 1 part polyethylene glycol (molecular weight 4000) and 4 parts diphenylmethane diisocyanate reacted at 80℃ for 2 hours, followed by the addition of 45 parts diphenylmethane diisocyanate and 50 parts polymethylene polyphenyl polyisocyanate. The blowing agent is a mixture of azobisisobutyronitrile and azodicarbonamide in a mass ratio of 5:1. The acid anhydride is tetrahydrophthalic anhydride.

[0052] The above-mentioned polyvinyl chloride, acid anhydride, modified isocyanate, catalyst, and heat stabilizer are mixed under vacuum to obtain a paste.

[0053] The paste is transferred to a molding machine and hot-pressed to obtain a molded bubble.

[0054] The molded foam is then subjected to secondary foaming, cross-linking, and curing in a moisture environment;

[0055] The above-mentioned cross-linked foam was cured in a water vapor environment to obtain rigid cross-linked polyvinyl chloride foam.

[0056] The molding pressure is 25 MPa, the molding temperature is 180℃, the molding time is 13 min, the secondary foaming temperature is 80℃, the foaming time is 3 hours, and the curing temperature is 65℃.

[0057] Comparative Example 1:

[0058] The raw materials, by mass fraction, consist of: 100 parts polyvinyl chloride; 70 parts isocyanate; 15 parts blowing agent; 15 parts acid anhydride; and 0 parts catalyst. The isocyanate is a mixture of 50 parts by mass of diphenylmethane diisocyanate and 50 parts by mass of polymethylene polyphenyl polyisocyanate. The blowing agent is a mixture of azobisisobutyronitrile and azodicarbonamide in a mass ratio of 5:1. The acid anhydride is methylhexahydrophthalic anhydride.

[0059] The above-mentioned polyvinyl chloride, acid anhydride, modified isocyanate, catalyst, and heat stabilizer are mixed under vacuum to obtain a paste.

[0060] The paste is transferred to a molding machine and hot-pressed to obtain a molded bubble.

[0061] The molded foam is then subjected to secondary foaming, cross-linking, and curing in a moisture environment;

[0062] The above-mentioned cross-linked foam was cured in a water vapor environment to obtain rigid cross-linked polyvinyl chloride foam.

[0063] The molding pressure is 20MPa, the molding temperature is 170℃, the molding time is 15min, the secondary foaming temperature is 95℃, the foaming time is 3 hours, and the curing temperature is 70℃.

[0064] Comparative Example 2:

[0065] The raw materials, by mass fraction, consist of: 100 parts polyvinyl chloride; 70 parts isocyanate; 15 parts blowing agent; 15 parts acid anhydride; and 1 part catalyst. The isocyanate is a mixture of 50 parts by mass of diphenylmethane diisocyanate and 50 parts by mass of polymethylene polyphenyl polyisocyanate. The blowing agent is a mixture of azobisisobutyronitrile and azodicarbonamide in a mass ratio of 5:1. The acid anhydride is methylhexahydrophthalic anhydride, and the catalyst is calcium stearate.

[0066] The above-mentioned polyvinyl chloride, acid anhydride, modified isocyanate, catalyst, and heat stabilizer are mixed under vacuum to obtain a paste.

[0067] The paste is transferred to a molding machine and hot-pressed to obtain a molded bubble.

[0068] The molded foam is then subjected to secondary foaming, cross-linking, and curing in a moisture environment;

[0069] The above-mentioned cross-linked foam was cured in a water vapor environment to obtain rigid cross-linked polyvinyl chloride foam.

[0070] The molding pressure is 20MPa, the molding temperature is 170℃, the molding time is 15min, the secondary foaming temperature is 95℃, the foaming time is 3 hours, and the curing temperature is 70℃.

[0071] Comparative Example 3:

[0072] The raw materials, by mass fraction, are: 100 parts polyvinyl chloride; 120 parts isocyanate; 20 parts blowing agent; 2 parts acid anhydride; and 1 part polyethylene glycol (molecular weight 8000). The isocyanate is diphenylmethane diisocyanate, the blowing agent is a mixture of azobisisobutyronitrile and azodicarbonamide in a mass ratio of 5:1, and the acid anhydride is a mixture of maleic anhydride and succinic anhydride in a mass ratio of 1:1.

[0073] The above-mentioned polyvinyl chloride, acid anhydride, modified isocyanate, catalyst, and heat stabilizer are mixed under vacuum to obtain a paste.

[0074] The paste is transferred to a molding machine and hot-pressed to obtain a molded bubble.

[0075] The molded foam is then subjected to secondary foaming, cross-linking, and curing in a moisture environment;

[0076] The above-mentioned cross-linked foam was cured in a water vapor environment to obtain rigid cross-linked polyvinyl chloride foam.

[0077] The molding pressure is 30MPa, the molding temperature is 200℃, the molding time is 5min, the secondary foaming temperature is 100℃, the foaming time is 1 hour, and the curing temperature is 50℃.

[0078] The table below shows the mechanical property results obtained from the tests:

[0079] sample density Compressive strength Shear strength Tensile strength Elongation at break ripening time Example 1 <![CDATA[89kg / m 3 ]]> 1.58MPa 1.11MPa 2.22MPa 25％ 9 days Example 2 <![CDATA[68kg / m 3 ]]> 1.35MPa 1.12MPa 1.62MPa 24％ 5 days Example 3 <![CDATA[50kg / m 3 ]]> 0.60MPa 0.53MPa 0.85MPa 14％ 11 days Example 4 <![CDATA[80kg / m 3 ]]> 1.58MPa 1.11MPa 2.22MPa 19％ 10 days Comparative Example 1 <![CDATA[67kg / m 3 ]]> 1.34MPa 1.10MPa 1.43MPa 14％ 15 days Comparative Example 2 <![CDATA[67kg / m 3 ]]> 1.33MPa 1.09MPa 1.43MPa 15％ 14 days Comparative Example 3 <![CDATA[48kg / m 3 ]]> 0.58MPa 0.50MPa 0.80MPa 14％ 13 days

[0080] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A rigid cross-linked polyvinyl chloride foam material, comprising the following components: 100 parts of polyvinyl chloride; 20-120 parts of modified isocyanate; 5-20 parts of blowing agent; 2-30 parts of acid anhydride; 0-1 parts of catalyst, wherein the modified isocyanate comprises 1%-10% by mass of isocyanate-terminated polyethylene glycol urethane and 90%-99% of one or more of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and carbodiimide modified isocyanate, wherein the polyethylene glycol has a molecular weight of 200-8000 and a functionality of 2.

2. The rigid cross-linked polyvinyl chloride foam material as described in claim 1, characterized in that, The modified isocyanate is obtained by mixing 1 part by weight of polyethylene glycol with 4-100 parts by weight of diisocyanate at 60-90°C for 0.5-4 hours, and adding 0-95 parts by weight of one or more of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and carbodiimide / urea ketone imide modified isocyanate and mixing them evenly.

3. The rigid cross-linked polyvinyl chloride foam material as described in claim 2, characterized in that, The modified isocyanate is obtained by mixing and reacting 1 part by weight of polyethylene glycol and 10-50 parts by weight of diphenylmethane diisocyanate at 60-90°C for 0.5-4 hours, and adding 0-95 parts by weight of one or more of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and carbodiimide / urea ketone imide modified isocyanate.

4. The rigid cross-linked polyvinyl chloride foam material according to any one of claims 1-3, characterized in that, The foaming agent is one or a mixture of two of azobisisobutyronitrile and azodicarbonamide.

5. The rigid cross-linked polyvinyl chloride foam material according to any one of claims 1-3, characterized in that, The acid anhydride is one or more of phthalic anhydride, maleic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and succinic anhydride.

6. The rigid cross-linked polyvinyl chloride foam material according to any one of claims 1-3, characterized in that, The catalyst is one or more of sodium octanoate, potassium octanoate, potassium stearate, and calcium stearate.

7. The method for preparing rigid cross-linked polyvinyl chloride foam material according to any one of claims 1-6, characterized in that, The method includes the following steps: (1) mixing the measured polyvinyl chloride, modified isocyanate, foaming agent, acid anhydride and catalyst evenly according to the ratio to obtain a paste mixture; (2) transferring the above paste mixture into a mold and hot pressing it; (3) cooling, depressurizing, opening the mold and taking out the molded foam from the mold; (4) placing the above molded foam in a water bath or steam environment for secondary foaming treatment to obtain secondary foamed foam; (5) placing the above secondary foamed foam in a steam environment for curing to obtain rigid cross-linked foam.

8. The preparation method according to claim 7, characterized in that, The hot pressing is carried out in a flat vulcanizing machine. The hot pressing pressure is 15-30 MPa, the hot pressing temperature is 150-200℃, and the hot pressing time is 5-20 min.

9. The preparation method according to claim 7 or 8, characterized in that, The secondary foaming process involves a water bath or steam temperature of 70-100℃ and a time of 1-4 hours.

10. The preparation method according to claim 7 or 8, characterized in that, Step (5) The curing temperature is 50-80℃ and the curing time is 5-12 days.

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