A kind of medical low-ammonia concentrated natural latex and preparation method thereof

Abstract

The invention belongs to the technical field of natural latex, specifically a kind of medical low-ammonia concentrated natural latex and a preparation method thereof, comprising the following steps: S1, filtering fresh latex to remove impurities and clots, then adding HY preservation system, centrifugation concentration, and obtaining latex and whey; S2, first adding fatty acid ammonium to the whey, mixing evenly and standing for 8-12 hours, then adding a mixture of sodium alginate, sodium oleate and phospholipids, mixing evenly and standing for 20-24 hours, taking the upper latex layer and centrifugation concentration, and obtaining modified whey; S3, mixing the latex obtained in step S1 and the modified whey obtained in step S2, then supplementing ammonia to a mass fraction of 0.1-0.2%, and then supplementing HY preservation system to obtain medical low-ammonia concentrated natural latex; the mass content of modified whey in the medical low-ammonia concentrated natural latex is 5-25%. By preparing modified whey, both the long-term mechanical stability of natural latex and the utilization rate of raw materials can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of natural latex, and in particular relates to a medical low-ammonia concentrated natural latex and a preparation method thereof. Background Art

[0002] Concentrated natural latex is obtained by separating excess water and impurities from latex particles through high-speed centrifugation of fresh latex. The main component is cis-1,4-polyisoprene rubber hydrocarbon, and the rest are non-rubber substances such as protein, fatty acids, ash, and sugars. Under normal circumstances, after natural latex leaves the rubber tree and is concentrated by centrifugation, its mechanical stability should be between 100-200s. After 3 months of natural storage, the mechanical stability gradually increases and should be able to reach the minimum limit of 650s specified in the "GB / T8289 Concentrated Natural Latex Ammonia Preservation Centrifugal or Pasted Latex Specification". Low mechanical stability can cause natural latex to easily thicken and flocculate during transportation, storage, and processing, and in severe cases it may even completely solidify.

[0003] It is generally believed that non-rubber substances such as lipids in natural latex are hydrolyzed under alkaline conditions to release fatty acids, which further react with ammonia in the latex to form ammonium carboxylates, which are adsorbed on the surface of rubber hydrocarbon particles, thereby keeping the natural latex stable and increasing its mechanical stability. However, the role of phospholipids depends on the ammonia content, and generally works better on concentrated natural latex with an ammonia content of 0.6-0.7%. Therefore, for low-ammonia concentrated natural latex, simply adding phospholipids cannot effectively improve its mechanical stability. Summary of the invention

[0004] The object of the present invention is to provide a medical low-ammonia concentrated natural latex and a preparation method thereof, so as to improve the mechanical stability of natural latex.

[0005] To achieve the above object, the present invention provides a method for preparing a medical low-ammonia concentrated natural latex, comprising the following steps:

[0006] S1, filtering the fresh latex to remove impurities and clots, then adding HY preservation system, centrifuging and concentrating to obtain latex and whey;

[0007] S2, first add fatty acid ammonium to the whey, mix well and let stand for 8 to 12 hours, then add a mixture of sodium alginate, sodium oleate and phospholipids, mix well and let stand for 20 to 24 hours, take the upper latex layer and centrifuge and concentrate to obtain modified whey;

[0008] S3, mixing the latex obtained in step S1 and the modified whey obtained in step S2, then adding ammonia to a mass fraction of 0.1-0.2%, and then adding HY preservation system to obtain medical low-ammonia concentrated natural latex;

[0009] The mass content of modified whey in the medical low-ammonia concentrated natural latex is 5-25%.

[0010] Furthermore, the fatty acid ammonium is one or more of ammonium stearate, ammonium oleate, and ammonium palmitate;

[0011] And / or, the amount of the fatty acid ammonium added is 0.1-0.3% of the mass of the whey.

[0012] Furthermore, the amount of sodium alginate added is 0.05-0.1% of the mass of the whey; the amount of sodium oleate added is 0.05-0.1% of the mass of the whey; and the amount of phospholipid added is 0.1-0.3% of the mass of the whey.

[0013] Furthermore, in step S3, 0.05-0.1% of the mass of medical low-ammonia concentrated natural latex lipase is added.

[0014] Furthermore, the HY preservation system consists of 1,3,5-trimethylhexahydro-s-triazine, sodium dodecyl sulfonate and KOH in a mass ratio of 3:2:1.

[0015] Furthermore, in step S1, the amount of 1,3,5-trimethylhexahydro-s-triazine added is 0.25-35% of the mass of the fresh latex; in step S3, the amount of 1,3,5-trimethylhexahydro-s-triazine added is 0.02-0.05% of the mass of the medical low-ammonia concentrated natural latex.

[0016] Furthermore, the mass content of modified whey in the medical low-ammonia concentrated natural latex is 15-20%.

[0017] Furthermore, the dry glue mass content of the fresh latex is 24-28%; the dry glue mass content of the medical low-ammonia concentrated natural latex is 60-68%.

[0018] Furthermore, the dry gelatin mass content of the modified whey is 30-35%.

[0019] The present invention also provides a medical low-ammonia concentrated natural latex, which is obtained by using any of the above preparation methods.

[0020] Compared with the prior art, the present invention mainly has the following technical advantages:

[0021] 1. The preparation method of the medical low-ammonia concentrated natural latex provided by the present invention comprises the following steps: coating the surface of rubber hydrocarbon particles in whey with fatty acid ammonium and phospholipids in sequence, and mixing them with latex for use, which can improve the raw material utilization rate of fresh latex on the one hand; on the other hand, the phospholipids in the outermost layer are gradually hydrolyzed to form long-chain fatty acids, which are combined with a small amount of ammonia water in the latex to generate fatty acid ammonium, which is adsorbed on the surface of rubber particles to improve mechanical stability; along with the hydrolysis of phospholipids, the fatty acid ammonium in the inner layer is gradually released and further adsorbed on the surface of rubber particles, which synergistically improves the mechanical stability and makes up for the problem of insufficient ammonia content. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The graphs are the change curves of the mechanical stability of Example 1 and Comparative Examples 1-3 over time. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] The preparation method of the medical low-ammonia concentrated natural latex provided by the present invention comprises the following steps:

[0025] S1, filtering the fresh latex to remove impurities and clots, then adding HY preservation system, centrifuging and concentrating to obtain latex and whey;

[0026] S2, first add fatty acid ammonium to the whey, mix well and let stand for 8 to 12 hours, then add a mixture of sodium alginate, sodium oleate and phospholipids, mix well and let stand for 20 to 24 hours, take the upper latex layer and centrifuge and concentrate to obtain modified whey;

[0027] S3, mixing the latex obtained in step S1 and the modified whey obtained in step S2, then adding ammonia to a mass fraction of 0.1-0.2% (relative to the total content of latex and modified whey), and then adding HY preservation system to obtain medical low-ammonia concentrated natural latex;

[0028] The mass content of modified whey in the medical low-ammonia concentrated natural latex is 5-25%.

[0029] Whey contains a small amount of unused rubber hydrocarbon particles. The method of the present invention can make these rubber hydrocarbon particles paste-formed and aggregated, thereby improving the utilization rate of raw materials. First, fatty acid ammonium is added, which can be adsorbed on the surface of rubber hydrocarbon particles to achieve preliminary paste-formation; then, sodium alginate, sodium oleate and phospholipids are added to continue to enhance the paste effect. At the same time, phospholipids are also adsorbed and coated on the surface of fatty acid ammonium to obtain multi-layer coated modified whey. Mixing it with latex can improve the raw material utilization rate of fresh latex on the one hand; on the other hand, the outermost layer of phospholipids is gradually hydrolyzed to form long-chain fatty acids, and combined with a small amount of ammonia water in the latex to generate fatty acid ammonium, which is adsorbed on the surface of rubber particles to improve mechanical stability. With the hydrolysis of phospholipids, the inner layer of fatty acid ammonium is gradually released and further adsorbed on the surface of rubber particles, synergistically improving mechanical stability and making up for the problem of insufficient ammonia content.

[0030] Furthermore, the fatty acid ammonium is one or more of ammonium stearate, ammonium oleate, and ammonium palmitate; and the added amount of the fatty acid ammonium is 0.1 to 0.3% of the mass of the whey.

[0031] Furthermore, the amount of sodium alginate added is 0.05-0.1% of the mass of the whey; the amount of sodium oleate added is 0.05-0.1% of the mass of the whey; the amount of phospholipid added is 0.1-0.3% of the mass of the whey. The phospholipid is soybean lecithin.

[0032] Furthermore, in step S3, 0.05-0.1% of the mass of medical low-ammonia concentrated natural latex is added with lipase, and the lipase is used to promote the hydrolysis of phospholipids, thereby improving the mechanical stability.

[0033] Furthermore, the HY preservation system consists of 1,3,5-trimethylhexahydro-s-triazine, sodium dodecyl sulfonate and KOH in a mass ratio of 3:2:1.

[0034] Furthermore, in step S1, the amount of 1,3,5-trimethylhexahydro-s-triazine added is 0.25-35% of the mass of the fresh latex; in step S3, the amount of 1,3,5-trimethylhexahydro-s-triazine added is 0.02-0.05% of the mass of the medical low-ammonia concentrated natural latex.

[0035] Furthermore, the mass content of modified whey in the medical low-ammonia concentrated natural latex is 15-20%.

[0036] Furthermore, the dry glue mass content of the fresh latex is 24-28%; the dry glue mass content of the medical low-ammonia concentrated natural latex is 60-68%.

[0037] Furthermore, the dry gelatin mass content of the modified whey is 30-35%.

[0038] Example 1

[0039] A method for preparing medical low-ammonia concentrated natural latex comprises the following steps:

[0040] S1. Filter the fresh latex (dry latex content is 26%) to remove impurities and clots, then add HY preservation system, centrifuge and concentrate to obtain latex and whey; wherein the HY preservation system consists of 1,3,5-trimethylhexahydro-s-triazine, sodium dodecyl sulfonate and KOH, and the added amounts are 0.3%, 0.2% and 0.1% of the mass of the fresh latex, respectively.

[0041] S2, first add ammonium oleate (added in an amount of 0.2% of the mass of the whey) to the whey, mix well and let stand for 12h, then add a mixture of sodium alginate (added in an amount of 0.08% of the mass of the whey), sodium oleate (added in an amount of 0.08% of the mass of the whey) and soy lecithin (added in an amount of 0.2% of the mass of the whey), mix well and let stand for 24h, take the upper latex layer by centrifugation and concentrate to obtain modified whey (dry glue mass content is 32%);

[0042] S3, mixing the latex obtained in step S1 and the modified whey obtained in step S2, then adding ammonia to a mass fraction of 0.15%, and then adding HY preservation system to obtain medical low-ammonia concentrated natural latex; wherein the HY preservation system is composed of 1,3,5-trimethylhexahydro-s-triazine, sodium dodecylsulfonate and KOH, and the added amounts are 0.03%, 0.02% and 0.01% of the mass of the medical low-ammonia concentrated natural latex respectively. The mass content of the modified whey in the medical low-ammonia concentrated natural latex is 15%.

[0043] Example 2

[0044] A method for preparing medical low-ammonia concentrated natural latex is different from Example 1 in that 0.06% of the mass of the medical low-ammonia concentrated natural latex lipase is also added in step S3.

[0045] Example 3

[0046] A method for preparing medical low-ammonia concentrated natural latex, which is different from Example 1 in that the amount of ammonium oleate added in step S2 is 0.1% of the mass of the whey.

[0047] Example 4

[0048] A method for preparing medical low-ammonia concentrated natural latex, which is different from Example 1 in that the amount of soybean lecithin added in step S2 is 0.1% of the mass of the whey.

[0049] Example 5

[0050] A method for preparing medical low-ammonia concentrated natural latex is different from Example 1 in that, in step S3, the mass content of modified whey in the medical low-ammonia concentrated natural latex is 5%.

[0051] Example 6

[0052] A method for preparing medical low-ammonia concentrated natural latex is different from that of Example 1 in that, in step S3, the mass content of modified whey in the medical low-ammonia concentrated natural latex is 25%.

[0053] Comparative Example 1

[0054] A method for preparing a medical low-ammonia concentrated natural latex, which is different from Example 1 in that step S2 comprises: adding a mixture of sodium alginate (added in an amount of 0.08% of the mass of the whey), sodium oleate (added in an amount of 0.08% of the mass of the whey) and soybean lecithin (added in an amount of 0.2% of the mass of the whey) to the whey, mixing evenly and standing for 24 hours, taking the upper latex layer for centrifugal concentration, and obtaining modified whey (dry glue mass content is 32%). The rest is the same as Example 1 and will not be repeated here.

[0055] Comparative Example 2

[0056] A method for preparing a medical low-ammonia concentrated natural latex, which is different from Example 1 in that step S2 comprises: first adding ammonium oleate (the amount added is 0.2% of the mass of the whey) to the whey, mixing evenly and letting it stand for 12 hours, then adding sodium alginate (the amount added is 0.08% of the mass of the whey) and sodium oleate (the amount added is 0.08% of the mass of the whey), mixing evenly and letting it stand for 24 hours, taking the upper latex layer for centrifugal concentration to obtain modified whey (the dry rubber mass content is 32%).

[0057] Comparative Example 3

[0058] A method for preparing a medical low-ammonia concentrated natural latex, which is different from Example 1 in that step S2 comprises: adding sodium alginate (the added amount is 0.08% of the mass of the whey) and sodium oleate (the added amount is 0.08% of the mass of the whey) to the whey, mixing them evenly and letting them stand for 24 hours, taking the upper latex layer and centrifuging and concentrating it to obtain modified whey (the dry rubber mass content is 32%).

[0059] The determination standard of dry glue content is GB / T8292-2008. The test standard of volatile fatty acids is GB / T8299-2008. The test standard of 30d mechanical stability is GB / T8301-2008.

[0060] Table 1 Test results of embodiments and comparative examples

[0061] Sample Dry content (%) Volatile acid (%) Machine stability (%) Example 1 61.26 0.011 1160 Example 2 60.78 0.013 1200 Example 3 60.87 0.013 1020 Example 4 60.92 0.015 1005 Example 5 61.38 0.012 992 Example 6 60.25 0.014 1098 Comparative Example 1 61.18 0.018 580 Comparative Example 2 61.02 0.015 517 Comparative Example 3 60.98 0.016 426

[0062] As can be seen from Table 1, the mechanical stability is significantly improved by adding an appropriate amount of modified whey to the latex. When a small amount of lipase is added, the mechanical stability is further improved. This is because lipase can promote the hydrolysis of phospholipids on the surface of the modified whey to generate long-chain fatty acids, and combine with a small amount of ammonia in the latex to generate fatty acid ammonium, which is adsorbed on the surface of the rubber particles to improve the mechanical stability. When the content of ammonium oleate or phospholipids in the modified whey is reduced, the mechanical stability decreases, but still meets the minimum limit requirements. When ammonium oleate and / or phospholipids are not adsorbed on the surface of the modified whey, the mechanical stability decreases significantly. Moreover, from Figure 1 It can be seen that when the outer layer is not adsorbed with phospholipids, the mechanical stability increases slowly, and the mechanical stability at 30 days is lower than that in Comparative Example 1.

[0063] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing medical low-ammonia concentrated natural latex, characterized in that: The following steps are involved: S1, filtering the fresh latex to remove impurities and clots, then adding HY preservation system, centrifuging and concentrating to obtain latex and whey; S2, first add fatty acid ammonium to the whey, mix well and let stand for 8-12h, then add a mixture of sodium alginate, sodium oleate and phospholipids, mix well and let stand for 20-24h, take the upper latex layer for centrifugation and concentration to obtain modified whey, wherein the fatty acid ammonium is one or more of ammonium stearate, ammonium oleate and ammonium palmitate; the amount of the fatty acid ammonium is 0.1-0.3% of the mass of the whey; the amount of the sodium alginate is 0.05-0.1% of the mass of the whey; the amount of the sodium oleate is 0.05-0.1% of the mass of the whey; the amount of the phospholipid is 0.1-0.3% of the mass of the whey; S3, mixing the latex obtained in step S1 and the modified whey obtained in step S2, then supplementing ammonia to a mass fraction of 0.1-0.2%, and then supplementing with a HY preservation system to obtain a medical low-ammonia concentrated natural latex, wherein the HY preservation system is composed of 1,3,5-trimethylhexahydro-s-triazine, sodium dodecylsulfonate and KOH in a mass ratio of 3:2:1; The mass content of modified whey in the medical low-ammonia concentrated natural latex is 5-25%.

2. The method for preparing the medical low-ammonia concentrated natural latex according to claim 1, characterized in that: In step S3, 0.05-0.1% of the mass of medical low-ammonia concentrated natural latex lipase is also added.

3. The method for preparing the medical low-ammonia concentrated natural latex according to claim 2, characterized in that: In step S1, the amount of 1,3,5-trimethylhexahydro-s-triazine added is 0.25-35% of the mass of the fresh latex; in step S3, the amount of 1,3,5-trimethylhexahydro-s-triazine added is 0.02-0.05% of the mass of the medical low-ammonia concentrated natural latex.

4. The method for preparing the medical low-ammonia concentrated natural latex according to claim 1, characterized in that: The mass content of modified whey in the medical low-ammonia concentrated natural latex is 15-20%.

5. The method for preparing the medical low-ammonia concentrated natural latex according to claim 1, characterized in that: The dry glue mass content of the fresh latex is 24-28%; the dry glue mass content of the medical low-ammonia concentrated natural latex is 60-68%.

6. The method for preparing the medical low-ammonia concentrated natural latex according to claim 1, characterized in that: The dry rubber mass content of the modified whey is 30-35%.

7. A medical low-ammonia concentrated natural latex, characterized in that: The method is obtained by the preparation method described in any one of claims 1 to 6.

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