Supercritical carbon dioxide foaming rubber material and preparation method thereof

Abstract

The invention discloses a supercritical carbon dioxide foamed rubber material and a preparation method thereof, and belongs to the technical field of foamed rubber. The foaming rubber is prepared from the following raw materials in parts by weight: 70 to 80 parts of natural rubber, 20 to 30 parts of chloroprene rubber, 20 to 30 parts of white carbon black, 4 to 5 parts of plasticizer, 1 to 1.5 parts of activating agent, 1 to 1.5 parts of coupling agent, 2 parts of anti-aging agent, 1.8 parts of sulfur, 3 to 4 parts of accelerant, 0.2 part of scorch retarder, 1 to 1.5 parts of potassium adipate, 5 parts of zinc oxide, 2 parts of magnesium oxide, 2 parts of stearic acid and 3.5 to 3.65 parts of supercritical carbon dioxide fluid. The continuous production of the rubber physical foaming sole can be realized, the foaming rubber vulcanization and foaming process can be completed by a one-time process, the size is basically stable after mold stripping, the sole can be used for subsequent shoemaking production without further processing, and the sole with relatively complex appearance size can be produced. The method is suitable for preparing the foamed rubber sole.

Description

Technical Field

[0001] The invention belongs to the technical field of foamed rubber and relates to a supercritical carbon dioxide foamed rubber material, in particular to a supercritical carbon dioxide foamed rubber material and a preparation method thereof. Background Art

[0002] Compared with dense rubber materials, foamed rubber materials have good cushioning, heat insulation, cold resistance and other properties, which can effectively reduce the weight of rubber products. There are two ways to foam rubber materials: physical foaming and chemical foaming.

[0003] Chemical foaming uses a foaming agent, which decomposes and produces gas when the rubber is heated. The gas forms closed or open cells inside the rubber, thereby achieving the purpose of foaming. Chemical foaming has the following problems: First, the size of the foam cells after rubber foaming is too large, generally 50-100μm, and even due to the dispersion of the foaming agent, the foam cell diameter may be greater than 100μm; second, chemical foaming will inevitably produce a mixture of closed cells and open cells, affecting the strength of the rubber product; third, the foaming agent, including the decomposition products of the foaming agent, will cause certain pollution to the environment.

[0004] There are currently two methods for physical foaming: microsphere foaming agent and supercritical foaming. Microsphere foaming agent expands when heated during the rubber vulcanization process to form holes, thereby achieving rubber foaming. However, this foaming method has the following problems: first, the bubbles are too large; second, it is difficult to achieve a foaming effect with a lower density. Supercritical foaming uses CO2, N2, etc. to enter the rubber colloid in a supercritical state. After the colloid is decompressed, the supercritical fluid becomes gas to form a foamed rubber product.

[0005] At present, the conventional method used in the industry to produce foamed rubber soles is that the rubber soles are initially vulcanized and then put into an autoclave to maintain the pressure so that the supercritical fluid can penetrate into the soles, and then the foamed rubber soles are formed after the pressure is reduced. Since there is no external mold control during the foaming process in this method, the size of the soles changes greatly after foaming, and further cutting is required, which makes continuous production impossible; and since the size change after foaming is unstable, it is difficult to produce soles with complex patterns or sizes. Summary of the invention

[0006] The purpose of the present invention is to provide a supercritical carbon dioxide foamed rubber material and a preparation method thereof, so as to solve the problem that the existing foamed insoles have large size changes after supercritical foaming and cannot be produced continuously.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A supercritical carbon dioxide foamed rubber material, the raw materials for making the same, in parts by weight, include: 70-80 parts of natural rubber, 20-30 parts of chloroprene rubber, 20-30 parts of white carbon black, 4-5 parts of plasticizer, 1-1.5 parts of activator, 1-1.5 parts of coupling agent, 2 parts of antioxidant, 1.8 parts of sulfur, 3-4 parts of accelerator, 0.2 parts of scorch retarder, 1-1.5 parts of potassium adipate, 5 parts of zinc oxide, 2 parts of magnesium oxide, 2 parts of stearic acid and 3.5-3.65 parts of supercritical carbon dioxide fluid;

[0009] The accelerators include accelerator CBS, accelerator DPG and accelerator ZDBDP.

[0010] As a limitation, the plasticizers include naphthenic oil and dibutyl phthalate.

[0011] As another limitation, the activating agent comprises polyethylene glycol.

[0012] As a third limitation, the coupling agent includes silane coupling agent Si-69.

[0013] As a fourth limitation, the antioxidant includes antioxidant 264 and antioxidant MP.

[0014] As a fifth limitation, the anti-scorching agent includes anti-scorching agent CTP.

[0015] The present invention also provides a method for preparing the above-mentioned supercritical carbon dioxide foamed rubber material, comprising the following steps:

[0016] S1. Mix natural rubber, chloroprene rubber, white carbon black, plasticizer, activator, coupling agent, antioxidant, accelerator CBS, anti-scorch agent, zinc oxide, magnesium oxide and stearic acid for internal kneading, control the temperature below 90°C, add sulfur, accelerator DPG, accelerator ZDTP and potassium adipate for mixing, and place for 24-48 hours to obtain a rubber strip;

[0017] S2. Preheat the rubber strip in the barrel of the injection machine, inject supercritical carbon dioxide fluid at a rate of 0.6-0.75L / min to form a rubber melt, and inject it into a vacuum vulcanization mold for foaming and vulcanization to obtain supercritical carbon dioxide foamed rubber.

[0018] As a limitation, the injection is into a vacuum vulcanization mold, the injection temperature is 108-112° C., and the injection speed is 3.8-4.2 g / s.

[0019] As another limitation, the vulcanization is carried out at a temperature of 153-157° C., a pressure of ≥15 MPa, and a time of 300-420 s.

[0020] As a third limitation, the preheating temperature is 85-90°C.

[0021] Due to the adoption of the above technical solution, the present invention has the following technical advances compared with the prior art:

[0022] ① The present invention provides a supercritical carbon dioxide foamed rubber material, in which potassium adipate and the side chain chlorine groups in chloroprene rubber can be cross-linked at a relatively low temperature, which ensures that when the supercritical carbon dioxide fluid is injected, the rubber melt has a certain strength, ensures the formation of a fine and dense closed-cell foam, and the pore distribution is more uniform; at the same time, the cross-linking reaction is reversible at high temperature (i.e., thermal reversible vulcanization), and after the rubber enters the vulcanization mold, the temperature rises and the chemical bonds are broken, so that the rubber flows and fills the mold normally and the outer skin of the sole is uniform;

[0023] ② The method for preparing a supercritical carbon dioxide foamed rubber material provided by the present invention can improve the strength of the rubber melt by adjusting the injection temperature and injection speed, so that the product is complete and defect-free. At the same time, by completing foaming and vulcanization shaping in the mold, the size of the sole is stable, and the pattern and size of the sole can be customized according to the mold;

[0024] ③ The preparation method of the supercritical carbon dioxide foamed rubber material provided by the present invention does not require further processing and can be directly used in subsequent shoe production, thus saving the operation process and being suitable for industrial production;

[0025] ④ The present invention provides a method for preparing a supercritical carbon dioxide foamed rubber material, which has a high material utilization rate. Since the foaming expansion size is stable, it does not require excessive cutting. After the original autoclave process foaming expansion, at least 10wt%-20wt% of the edge material needs to be removed, while the product of this method only has the flow edge generated during the vulcanization process, and only 3wt%-5wt% of the material needs to be cut.

[0026] The invention can realize continuous production of rubber physical foaming soles, complete the vulcanization and foaming process of the foamed rubber in one process, and the size is basically stable after leaving the mold, and can be used for subsequent shoe production without further processing, and can also produce soles with relatively complex appearance and size. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below by specific examples. It should be understood that the described examples are only used to explain the present invention, and are not intended to limit the present invention.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art.

[0029] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0030] Examples 1-5

[0031] This embodiment prepares five kinds of rubber soles made of supercritical carbon dioxide foamed rubber materials, also provides comparative examples, and tests relevant properties, specifically including the following steps performed in sequence:

[0032] (I) Sample preparation

[0033] Embodiment 1:

[0034] S1. 80kg natural rubber, 20kg chloroprene rubber, 30kg white carbon black, 4kg plasticizer (3kg cyclohexane and 1kg dibutyl phthalate (DBP)), 1kg polyethylene glycol, 1kg silane coupling agent Si-69, 2kg antioxidant (1kg antioxidant 264 and 1kg antioxidant MP), 1kg accelerator CBS, 0.2kg scorch retarder CTP, 5kg zinc oxide, 2kg active magnesium oxide and 2kg stearic acid were mixed and added to a banbury mixer for banbury mixing. After the banbury mixing was completed, an open rubber mixer was used to control the rubber temperature to 85°C, 1.8kg sulfur, 1kg accelerator DPG, 1kg accelerator ZDTP and 1kg potassium adipate were added for mixing, and the mixed rubber was placed for 24h to obtain a rubber strip;

[0035] S2. Add the rubber strip to the injection port of the injection machine. The temperature of the injection machine barrel is controlled at 85°C. The rubber strip is preheated and softened in the injection machine barrel. 3.5 kg of supercritical carbon dioxide fluid is injected at a rate of 0.6 L / min to form a rubber melt. The temperature of the injection port of the injection machine is controlled at 108°C. The rubber melt is injected into the vacuum vulcanization mold at an injection rate of 3.8 g / s. It is foamed at 153°C and 15 MPa and vulcanized for 300 s to obtain supercritical carbon dioxide foamed rubber ɑ1.

[0036] Embodiment 2-5:

[0037] Examples 2-5 respectively prepared supercritical carbon dioxide foamed rubbers ɑ2-ɑ5, and their preparation methods were basically the same as those of supercritical carbon dioxide foamed rubber ɑ1, except for the differences in the amounts of some raw materials and process parameters. The raw material process parameters of supercritical carbon dioxide foamed rubbers ɑ2-ɑ5 are shown in Table 1:

[0038] Table 1 List of raw materials and processes

[0039]

[0040]

[0041] Comparative Example 1:

[0042] Comparative Example 1 adopts a traditional preparation process, that is, after the rubber sole is initially vulcanized, it enters an autoclave, maintains pressure to allow the supercritical fluid to penetrate into the sole, and forms a foamed rubber sole after decompression. Specifically, the following steps are performed in sequence:

[0043] S1. 100kg natural rubber, 30kg white carbon black, 4kg plasticizer (3kg cyclohexane and 1kg dibutyl phthalate), 1kg polyethylene glycol, 1kg silane coupling agent Si-69, 2kg antioxidant (1kg antioxidant 264 and 1kg antioxidant MP), 1kg accelerator CBS, 0.2kg scorch retarder CTP, 5kg zinc oxide, 2kg active magnesium oxide and 2kg stearic acid were mixed and added to a banbury mixer for banbury mixing. After the banbury mixing was completed, an open rubber mixer was used to control the rubber temperature to 85°C, 1.8kg sulfur, 1kg accelerator DPG, 1kg accelerator ZDTP and 1kg potassium adipate were added for mixing, and the mixed rubber was placed for 24h to obtain a rubber strip;

[0044] S2. Add the rubber strip to the rubber inlet of the injection machine, control the temperature of the injection machine barrel at 85°C, preheat and soften the rubber strip in the injection machine barrel, control the temperature of the injection port of the injection machine at 100°C, inject the rubber melt into the vacuum vulcanization mold at an injection speed of 3.8g / s, and vulcanize at 153°C and 15MPa for 300s to obtain a pre-vulcanized unfoamed rubber sole;

[0045] S3. The rubber sole was put into an autoclave, 3.5 kg of supercritical carbon dioxide fluid was added, the pressure was maintained at 140 ° C and 18 MPa for 3 h, the pressure was released and cooled to obtain a foamed rubber sole;

[0046] S4. Place the foamed rubber sole in a drying oven and perform secondary vulcanization (vulcanization at 150° C. for 8 min) using hot air to obtain a supercritical carbon dioxide foamed rubber sole B1.

[0047] Comparative Example 2:

[0048] The preparation process of Comparative Example 2 is basically the same as that of Example 1, except that potassium adipate is not added in Comparative Example 2 to verify the effect of thermal reversible vulcanization. Specifically, the following steps are performed in sequence:

[0049] S1. 80kg natural rubber, 20kg chloroprene rubber, 30kg white carbon black, 4kg plasticizer (3kg cyclohexane and 1kg dibutyl phthalate), 1kg polyethylene glycol, 1kg silane coupling agent Si-69, 2kg antioxidant (1kg antioxidant 264 and 1kg antioxidant MP), 1kg accelerator CBS, 0.2kg scorch retarder CTP, 5kg zinc oxide, 2kg active magnesium oxide and 2kg stearic acid were mixed and added to a banbury mixer for banbury mixing. After the banbury mixing was completed, an open rubber mixer was used to control the rubber temperature to 85°C, 1.8kg sulfur, 1kg accelerator DPG and 1kg accelerator ZDTP were added for mixing, and the mixed rubber was placed for 24h to obtain a rubber strip;

[0050] S2. Add the rubber strip to the injection port of the injection machine. The temperature of the injection machine barrel is controlled at 85°C. The rubber strip is preheated and softened in the injection machine barrel. 3.5 kg of supercritical carbon dioxide fluid is injected at a rate of 0.6 L / min to form a rubber melt. The temperature of the injection port of the injection machine is controlled at 108°C. The rubber melt is injected into the vacuum vulcanization mold at an injection rate of 3.8 g / s. Vulcanize at 153°C and 15 MPa for 300 s to obtain supercritical carbon dioxide foamed rubber B2.

[0051] (II) Performance test of supercritical carbon dioxide foamed rubber materials

[0052] Take supercritical carbon dioxide foamed rubbers ɑ1-ɑ5, and supercritical carbon dioxide foamed rubbers B1 and B2, and test the density, hardness, tensile strength, tear strength and elongation at break of the foamed rubber according to "HG / T 2872-2009 Test method for apparent density of microporous materials for rubber and plastic shoes", "HG / T2489-2007 Test method for hardness of microporous materials for shoes", "GB / T 10654-2001 Determination of tensile strength and elongation at break of polymer porous elastic materials", "GB / T529-2008 Determination of tear strength of vulcanized rubber or thermoplastic rubber (trouser-shaped, right-angled and crescent-shaped specimens)" and "GB / T10654-2001 Determination of tensile strength and elongation at break of polymer porous elastic materials", respectively. The results are shown in Table 2:

[0053] Table 2 Performance test results

[0054]

[0055]

[0056] It can be seen from Table 2 that if potassium adipate is not added, that is, potassium adipate cannot undergo thermally reversible vulcanization with the side chain chlorine groups in the chloroprene rubber, the hardness, tensile strength, tear strength, etc. of the produced rubber foam sole B2 cannot meet the standard requirements and the physical properties are poor.

[0057] The rubber foam sole B1 produced by the traditional process method, although the physical properties can reach the standard, the foaming process is uncontrolled because there is no restriction of the mold during the foaming process, and the rubber sole after foaming is severely deformed and unstable in size. It needs to be cut again according to the mold size requirements, which greatly wastes raw materials and cannot produce soles with more complex patterns (the method in the present invention can directly carve patterns on the mold, and the foaming and vulcanization processes are all carried out in the mold, and the rubber foam soles that meet the size and pattern requirements can be directly produced). At the same time, since the traditional process production method needs to increase the cutting step, the production efficiency is greatly reduced in actual production, and 300-350 pairs of soles are produced per shift on average, while the soles produced by the method of the present invention can produce more than 400 pairs of soles per shift on average.

Claims

1. A supercritical carbon dioxide foamed rubber material, characterized in that: The raw materials used to make it include, by weight: 70-80 parts of natural rubber, 20-30 parts of chloroprene rubber, 20-30 parts of white carbon black, 4-5 parts of plasticizer, 1-1.5 parts of activator, 1-1.5 parts of coupling agent, 2 parts of antioxidant, 1.8 parts of sulfur, 3-4 parts of accelerator, 0.2 parts of scorch retarder, 1-1.5 parts of potassium adipate, 5 parts of zinc oxide, 2 parts of magnesium oxide, 2 parts of stearic acid and 3.5-3.65 parts of supercritical carbon dioxide fluid; The accelerators include accelerator CBS, accelerator DPG and accelerator ZDBDP.

2. A supercritical carbon dioxide foamed rubber material according to claim 1, characterized in that: The plasticizers include naphthenic oil and dibutyl phthalate.

3. A supercritical carbon dioxide foamed rubber material according to claim 1 or 2, characterized in that: The activating agent includes polyethylene glycol.

4. A supercritical carbon dioxide foamed rubber material according to claim 1 or 2, characterized in that: The coupling agent includes silane coupling agent Si-69.

5. A supercritical carbon dioxide foamed rubber material according to claim 1 or 2, characterized in that: The antioxidants include antioxidant 264 and antioxidant MP.

6. A supercritical carbon dioxide foamed rubber material according to claim 1 or 2, characterized in that: The anti-scorching agent includes an anti-scorching agent CTP.

7. A method for preparing a supercritical carbon dioxide foamed rubber material according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Mix natural rubber, chloroprene rubber, white carbon black, plasticizer, activator, coupling agent, antioxidant, accelerator CBS, anti-scorch agent, zinc oxide, magnesium oxide and stearic acid for internal kneading, control the temperature below 90°C, add sulfur, accelerator DPG, accelerator ZDTP and potassium adipate for mixing, and place for 24-48 hours to obtain a rubber strip; S2. Preheat the rubber strip in the barrel of the injection machine, inject supercritical carbon dioxide fluid at a rate of 0.6-0.75 L / min to form a rubber melt, and inject it into a vacuum vulcanization mold for foaming and vulcanization to obtain supercritical carbon dioxide foamed rubber.

8. The preparation method according to claim 7, characterized in that: The injection is carried out into a vacuum vulcanization mold, the injection temperature is 108-112° C., and the injection speed is 3.8-4.2 g / s.

9. The preparation method according to claim 7 or 8, characterized in that: The vulcanization temperature is 153-157° C., the pressure is ≥15 MPa, and the time is 300-420 seconds.

10. The preparation method according to claim 7 or 8, characterized in that: The preheating temperature is 85-90°C.

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