A composite stabilizer for chlorinated alkanes, preparation method and application thereof

Abstract

The present invention belongs to the technical field of rubber additive manufacturing, and specifically relates to a composite stabilizer of chlorinated alkanes, a preparation method and an application. The raw materials of the stabilizer include the following components: carbon nanotube-modified epoxy resin, epoxy soybean oil, metal soap, anti-aging agent, antioxidant, auxiliary agent and dispersant. The preparation method includes first adding carbon nanotube-modified epoxy resin, epoxy soybean oil and auxiliary agent to a part of the dispersant to obtain mixture 1; then adding metal soap, anti-aging agent and antioxidant to the remaining dispersant to mix and disperse evenly; obtaining mixture 2; finally, adding mixture 1 to mixture 2 to mix. The present invention adopts carbon nanotube-modified epoxy resin and epoxy soybean oil for compounding, and the other raw materials are effectively coordinated to maintain the ultra-high stability of chlorinated paraffin.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber additive manufacturing, and specifically relates to a composite stabilizer of chlorinated alkane, a preparation method and application thereof. Background Art

[0002] Chlorinated alkanes are made from alkanes through chlorination. Chlorinated alkanes have good flame retardant properties, anti-aging, antistatic, good electrical insulation and material compatibility, and are inexpensive. Therefore, they are widely used in rubber tapes, tires, automotive floors, cables, coatings, paints, adhesives and other fields with flame retardant requirements as additives to improve performance, so that the main product has good flame retardant properties. They are also used in fireworks and firecrackers.

[0003] In the process of processing rubber and plastic products, a series of processes such as mixing, rubber refining, and extrusion are generally required. These processing steps often have a certain degree of temperature rise, and the temperature rise generated by different products during the processing is also different, and some can even reach more than 200°C. Therefore, there is a requirement for thermal stability of chlorinated alkanes. In the process of processing, due to the effect of temperature, chlorinated alkanes will decompose to varying degrees, and the higher the temperature and the longer the processing time, the more serious the decomposition. The decomposition of chlorinated alkanes not only causes the loss of effective ingredients, changes the formula ratio, and affects the flame retardant effect, but the decomposition and carbonization of chlorinated alkanes will also darken the color of the main product, increase the acidity, generate bubbles, and even corrode the surface of the machine to produce sticking phenomenon, making processing difficult and reducing product performance.

[0004] According to industry standards, the thermal stability of general chlorinated alkanes is sufficient to meet the needs of general-purpose products.

[0005] However, there is a demand for high-end products both at home and abroad, which places stringent requirements on the thermal stability of chlorinated alkanes.

[0006] Chinese invention patent application 201610715887.1 discloses a chlorinated paraffin composite stabilizer, which belongs to the field of stabilizer technology. It is made by mixing ethylene glycol diglycidyl ether, composite rare earth stabilizer, phosphite, composite antioxidant, p-methoxyphenol, and ethylene bisstearamide; wherein the weight ratio of ethylene glycol diglycidyl ether, composite rare earth stabilizer, and phosphite is 42-60:10:5-6; the composite antioxidant accounts for 1-2% of the total weight of the stabilizer; p-methoxyphenol accounts for 1-2% of the total weight of the stabilizer; ethylene bisstearamide accounts for 1-3% of the total weight of the stabilizer, and all raw materials can be mixed during production. The stabilizer has good compatibility with chlorinated paraffin and can increase the thermal decomposition temperature and UV stability of chlorinated paraffin.

[0007] Another Chinese invention patent application 202011488221.X discloses a multifunctional new type of chlorinated paraffin liquid composite sunscreen and its preparation method. The composite sunscreen consists of 70-80 parts of solvent, 8-12 parts of anti-ultraviolet agent KS-1, 3-5 parts of benzotriazole anti-ultraviolet agent, 2-5 parts of light stabilizer, 2-5 parts of antioxidant, and 0-3 parts of fluorescent whitening agent. The present invention not only overcomes the shortcomings of adding a small molecule single anti-ultraviolet agent, such as large addition amount, difficulty in dispersion, high use cost, and poor sunscreen effect, but also can absorb hydrogen chloride through the secondary amine group on the KS-1 structure to improve the thermal stability of chlorinated paraffin. The product preparation process is simple, the yield is high, the anti-sunscreen effect is outstanding in chlorinated paraffin, the raw materials are easy to obtain, and it has potential market application value.

[0008] The above technologies have studied the thermal stability of chlorinated alkanes, and the stability has been improved to a certain extent. However, the comprehensive performance of improving the thermal stability and light stability of chlorinated paraffins needs to be further improved. Summary of the invention

[0009] In view of the deficiencies in the prior art, the present invention provides a composite stabilizer for chlorinated alkanes, a preparation method and applications thereof.

[0010] In order to achieve the purpose of the present invention, the technical solution adopted is as follows:

[0011] A composite stabilizer for chlorinated alkanes. The raw materials of the stabilizer include the following components: carbon nanotube-modified epoxy resin, epoxy soybean oil, metal soap, anti-aging agent, antioxidant, auxiliary agent and dispersant.

[0012] Preferably, the raw materials of the stabilizer include the following components by weight: 15-25 parts of carbon nanotube-modified epoxy resin, 15-25 parts of epoxidized soybean oil, 0.5-1 parts of metal soap, 5-10 parts of anti-aging agent, 1-5 parts of antioxidant, 1-5 parts of auxiliary agent and 30-60 parts of dispersant.

[0013] Preferably, the auxiliary agent is selected from one or more of glyceryl monostearate, sucrose ester, polyoxyethylene fatty acid ester and lecithin.

[0014] Preferably, the auxiliary agent is a mixture of sucrose ester and lecithin in a mass ratio of 1:3-5.

[0015] Preferably, the antioxidant is selected from one or more of HP136, 1010, and 168.

[0016] Preferably, the anti-aging agent comprises a mixture of nano-silicon dioxide and nano-titanium dioxide in a mass ratio of 0.2-0.6:1.

[0017] Preferably, the metal soap is selected from one or more of magnesium stearate, aluminum stearate, calcium stearate and zinc stearate.

[0018] Preferably, the dispersant is selected from at least one of sodium lauryl sulfate, sodium dodecylbenzene sulfonate, dioctyl sodium sulfosuccinate, poloxamer 188, polyoxyethylene 400 monolaurate, polyoxyethylene hydrogenated castor oil, and polyoxyethylene nonylphenol ether.

[0019] Another object of the present invention is to provide a method for preparing the composite stabilizer, comprising the following steps:

[0020] (1) adding carbon nanotube-modified epoxy resin, epoxy soybean oil and an auxiliary agent to a portion of the dispersant and mixing to obtain a mixture 1;

[0021] (2) adding the metal soap, anti-aging agent and antioxidant to the remaining dispersant and mixing and dispersing them uniformly to obtain a mixture 2;

[0022] (3) Add mixture 1 into mixture 2 and mix.

[0023] Preferably, the partial dispersant in step (1) is 60-75% dispersant; the mixing temperature is 70-90°C; and the mixing temperature in step (2) is 65-75°C.

[0024] The third object of the present invention is to provide the use of the above composite stabilizer in preparing chlorinated alkanes with improved stability.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention adopts carbon nanotubes to modify epoxy resin, which can appropriately include chlorinated alkanes, etc., to prevent them from reacting to light, heat, etc., and the epoxy resin is compounded with epoxidized soybean oil to effectively synergize and maintain the ultra-high stability of chlorinated paraffin.

[0027] (2) The present invention further uses a specific metal soap, which not only makes the surface of the stabilizer smooth, but also promotes more uniform mixing of raw materials during the preparation process.

[0028] (3) The present invention adopts a specific anti-aging agent and an antioxidant in combination, which significantly improves the light stability of chlorinated paraffin.

[0029] (4) The auxiliary agent of the present invention can not only promote the carbon nanotube-modified epoxy resin and metal soap to improve the stability of chlorinated paraffin, but also cooperate with the dispersant to improve the stability of the stabilizer. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with specific embodiments. The raw materials in the following embodiments are all commercially available conventional materials. Among them, the supplier of carbon nanotube-modified epoxy resin is Shanghai Yihui Biotechnology Co., Ltd., the supplier of epoxy soybean oil is Shanghai Yuanye Biotechnology Co., Ltd., the product number is S50881, and the supplier of sucrose ester is Beijing Kangruina Biotechnology Co., Ltd., the product number is A3046;

[0031] Example 1

[0032] The raw materials of the chlorinated alkane stabilizer of this embodiment are composed of the following components in parts by weight: 15 parts of carbon nanotube-modified epoxy resin, 15 parts of epoxidized soybean oil, 0.5 parts of metal soap, 5 parts of antioxidant, 1 part of antioxidant, 1 part of auxiliary agent and 30 parts of dispersant.

[0033] The auxiliary agent is a mixture of sucrose ester and lecithin in a mass ratio of 1:3;

[0034] The antioxidant agent is a mixture of HP136 and 1010 in a mass ratio of 1:1;

[0035] The anti-aging agent is a mixture of nano silicon dioxide and nano titanium dioxide in a mass ratio of 0.2:1;

[0036] The metal soap has a mass ratio of aluminum stearate to zinc stearate = 1:3;

[0037] The dispersant is a mixture of sodium dodecylbenzene sulfonate, sodium dioctyl succinate sulfonate and polyoxyethylene hydrogenated castor oil in a mass ratio of 1:1:0.5.

[0038] The preparation method is as follows:

[0039] (1) adding carbon nanotube-modified epoxy resin, epoxy soybean oil and additives to 60% dispersant, and mixing at 70° C. until uniformly dispersed to obtain mixture 1;

[0040] (2) adding metal soap, anti-aging agent and antioxidant to the remaining dispersant, mixing and dispersing them uniformly at 65° C. to obtain mixture 2;

[0041] (3) Add mixture 1 to mixture 2 and mix at 350 rpm until the mixture is evenly dispersed.

[0042] Example 2

[0043] The raw materials of the chlorinated alkane stabilizer of this embodiment are composed of the following components in parts by weight: 25 parts of carbon nanotube-modified epoxy resin, 25 parts of epoxidized soybean oil, 1 part of metal soap, 10 parts of anti-aging agent, 5 parts of antioxidant, 5 parts of auxiliary agent and 60 parts of dispersant.

[0044] The auxiliary agent is a mixture of sucrose ester and lecithin in a mass ratio of 1:5;

[0045] The antioxidant agent is a mixture of HP136 and 168 in a mass ratio of 3:1;

[0046] The anti-aging agent is a mixture of nano silicon dioxide and nano titanium dioxide in a mass ratio of 0.6:1;

[0047] The metal soap is aluminum stearate:zinc stearate=1:3;

[0048] The dispersant is a mixture of sodium dodecylbenzene sulfonate, sodium dioctyl succinate sulfonate and polyoxyethylene hydrogenated castor oil in a mass ratio of 1:1:0.5.

[0049] The preparation method is as follows:

[0050] (1) adding carbon nanotube-modified epoxy resin, epoxy soybean oil and additives to 75% dispersant, and mixing at 90° C. until uniformly dispersed to obtain mixture 1;

[0051] (2) adding metal soap, anti-aging agent and antioxidant to the remaining dispersant, mixing and dispersing them uniformly at 75° C. to obtain mixture 2;

[0052] (3) Add mixture 1 to mixture 2 and mix at 350 rpm until the mixture is evenly dispersed.

[0053] Example 3

[0054] The raw materials of the chlorinated alkane stabilizer of this embodiment are composed of the following components in parts by weight: 20 parts of carbon nanotube-modified epoxy resin, 20 parts of epoxidized soybean oil, 0.8 parts of metal soap, 8 parts of anti-aging agent, 3 parts of antioxidant, 2 parts of auxiliary agent and 45 parts of dispersant.

[0055] The auxiliary agent is a mixture of sucrose ester and lecithin in a mass ratio of 1:4;

[0056] The antioxidant agent is a mixture of HP136, 1010, and 168 in a mass ratio of 1:3:0.3;

[0057] The anti-aging agent is a mixture of nano silicon dioxide and nano titanium dioxide in a mass ratio of 0.5:1;

[0058] The metal soap is aluminum stearate:zinc stearate=1:3;

[0059] The dispersant is a mixture of sodium dodecylbenzene sulfonate, sodium dioctyl succinate sulfonate, and polyoxyethylene 400 monolaurate in a mass ratio of 1:2:5.

[0060] The preparation method is as follows:

[0061] (1) adding carbon nanotube-modified epoxy resin, epoxy soybean oil and additives to 65% dispersant, and mixing at 80° C. until uniformly dispersed to obtain mixture 1;

[0062] (2) adding metal soap, anti-aging agent and antioxidant to the remaining dispersant, mixing and dispersing them uniformly at 70° C. to obtain mixture 2;

[0063] (3) Add mixture 1 to mixture 2 and mix at 350 rpm until the mixture is evenly dispersed.

[0064] Example 4

[0065] The raw materials of the chlorinated alkane stabilizer of this embodiment are composed of the following components in parts by weight: 22 parts of carbon nanotube-modified epoxy resin, 18 parts of epoxidized soybean oil, 0.5 parts of metal soap, 10 parts of anti-aging agent, 1 part of antioxidant, 4 parts of auxiliary agent and 40 parts of dispersant.

[0066] The auxiliary agent is a mixture of sucrose ester and lecithin in a mass ratio of 1:3;

[0067] The antioxidant is a mixture of HP136 and 1010 in a mass ratio of 1:1;

[0068] The antioxidant aluminum stearate:zinc stearate=1:3;

[0069] The dispersant is a mixture of sodium dodecylbenzene sulfonate, sodium dioctyl sulfosuccinate and polyoxyethylene 400 monolaurate in a mass ratio of 1:2:5.

[0070] The preparation method is as follows:

[0071] (1) adding carbon nanotube-modified epoxy resin, epoxy soybean oil and additives to 65% dispersant, and mixing at 75° C. until uniformly dispersed to obtain mixture 1;

[0072] (2) adding metal soap, anti-aging agent and antioxidant to the remaining dispersant, mixing and dispersing them uniformly at 70° C. to obtain mixture 2;

[0073] (3) Add mixture 1 to mixture 2 and mix at 350 rpm until the mixture is evenly dispersed.

[0074] The following are some of the stabilizer compositions that were eliminated during the experiment:

[0075] Comparative Example 1

[0076] The raw materials of the chlorinated alkane stabilizer in this comparative example are composed of the following components in parts by weight: 30 parts of epoxidized soybean oil, 0.5 parts of metal soap, 5 parts of anti-aging agent, 1 part of antioxidant, 1 part of auxiliary agent and 30 parts of dispersant.

[0077] The auxiliary agent is a mixture of sucrose ester and lecithin in a mass ratio of 1:3;

[0078] The antioxidant agent is a mixture of HP136 and 1010 in a mass ratio of 1:1;

[0079] The anti-aging agent is a mixture of nano silicon dioxide and nano titanium dioxide in a mass ratio of 0.2:1;

[0080] The metal soap is aluminum stearate:zinc stearate=1:3;

[0081] The dispersant is a mixture of sodium dodecylbenzene sulfonate, sodium dioctyl succinate sulfonate and polyoxyethylene hydrogenated castor oil in a mass ratio of 1:1:0.5.

[0082] The preparation method is as follows:

[0083] (1) adding carbon nanotube-modified epoxy resin, epoxy soybean oil and additives to 60% dispersant, and mixing at 70° C. until uniformly dispersed to obtain mixture 1;

[0084] (2) adding metal soap, anti-aging agent and antioxidant to the remaining dispersant, mixing and dispersing them uniformly at 65° C. to obtain mixture 2;

[0085] (3) Add mixture 1 to mixture 2 and mix at 350 rpm until the mixture is evenly dispersed.

[0086] Comparative Example 2

[0087] The raw materials of the chlorinated alkane stabilizer of this embodiment are composed of the following components in parts by weight: 30 parts of carbon nanotube-modified epoxy resin, 0.5 parts of metal soap, 5 parts of anti-aging agent, 1 part of antioxidant, 1 part of auxiliary agent and 30 parts of dispersant.

[0088] The auxiliary agent is a mixture of sucrose ester and lecithin in a mass ratio of 1:3;

[0089] The antioxidant agent is a mixture of HP136 and 1010 in a mass ratio of 1:1;

[0090] The anti-aging agent is a mixture of nano silicon dioxide and nano titanium dioxide in a mass ratio of 0.2:1;

[0091] The metal soap is aluminum stearate:zinc stearate=1:3;

[0092] The dispersant is a mixture of sodium dodecylbenzene sulfonate, sodium dioctyl succinate sulfonate and polyoxyethylene hydrogenated castor oil in a mass ratio of 1:1:0.5.

[0093] The preparation method is as follows:

[0094] (1) adding carbon nanotube-modified epoxy resin, epoxy soybean oil and additives to 60% dispersant, and mixing at 70° C. until uniformly dispersed to obtain mixture 1;

[0095] (2) adding metal soap, anti-aging agent and antioxidant to the remaining dispersant, mixing and dispersing them uniformly at 65° C. to obtain mixture 2;

[0096] (3) Add mixture 1 to mixture 2 and mix at 350 rpm until the mixture is evenly dispersed.

[0097] Comparative Example 3

[0098] The raw materials of the chlorinated alkane stabilizer of this embodiment are composed of the following components in parts by weight: 15 parts of carbon nanotube-modified epoxy resin, 15 parts of epoxidized soybean oil, 0.5 parts of metal soap, 5 parts of antioxidant, 1 part of antioxidant, 1 part of auxiliary agent and 60 parts of dispersant.

[0099] The auxiliary agent is lecithin;

[0100] The antioxidant agent is a mixture of HP136 and 1010 in a mass ratio of 1:1;

[0101] The anti-aging agent is a mixture of nano silicon dioxide and nano titanium dioxide in a mass ratio of 0.2:1;

[0102] The metal soap is aluminum stearate:zinc stearate=1:3;

[0103] The dispersant is a mixture of sodium dodecylbenzene sulfonate, sodium dioctyl succinate sulfonate and polyoxyethylene hydrogenated castor oil in a mass ratio of 1:1:0.5.

[0104] The preparation method is as follows:

[0105] (1) adding carbon nanotube-modified epoxy resin, epoxy soybean oil and additives to 60% dispersant, and mixing at 70° C. until uniformly dispersed to obtain mixture 1;

[0106] (2) adding metal soap, anti-aging agent and antioxidant to the remaining dispersant, mixing and dispersing them uniformly at 65° C. to obtain mixture 2;

[0107] (3) Add mixture 1 to mixture 2 and mix at 350 rpm until the mixture is evenly dispersed.

[0108] Comparative Example 4

[0109] The raw materials of the chlorinated alkane stabilizer of this embodiment are composed of the following components: 15 parts of carbon nanotube-modified epoxy resin, 15 parts of epoxidized soybean oil, 0.5 parts of metal soap, 5 parts of antioxidant, 1 part of antioxidant, 1 part of auxiliary agent and 60 parts of dispersant.

[0110] The auxiliary agent is sucrose ester;

[0111] The antioxidant agent is a mixture of HP136 and 1010 in a mass ratio of 1:1;

[0112] The anti-aging agent is a mixture of nano silicon dioxide and nano titanium dioxide in a mass ratio of 0.2:1;

[0113] The metal soap is aluminum stearate:zinc stearate=1:3;

[0114] The dispersant is a mixture of sodium dodecylbenzene sulfonate, sodium dioctyl succinate sulfonate and polyoxyethylene hydrogenated castor oil in a mass ratio of 1:1:0.5.

[0115] The preparation method is as follows:

[0116] (1) adding carbon nanotube-modified epoxy resin, epoxy soybean oil and additives to 60% dispersant, and mixing at 70° C. until uniformly dispersed to obtain mixture 1;

[0117] (2) adding metal soap, anti-aging agent and antioxidant to the remaining dispersant, mixing and dispersing them uniformly at 65° C. to obtain mixture 2;

[0118] (3) Add mixture 1 to mixture 2 and mix at 350 rpm until the mixture is evenly dispersed.

[0119] Comparative Example 5

[0120] The raw materials of the chlorinated alkane stabilizer of this comparative example are composed of the following components in parts by weight: 15 parts of carbon nanotube-modified epoxy resin, 15 parts of epoxidized soybean oil, 0.5 parts of metal soap, 5 parts of anti-aging agent, 1 part of antioxidant, 1 part of auxiliary agent and 60 parts of dispersant.

[0121] The auxiliary agent is a mixture of sucrose ester and lecithin in a mass ratio of 1:3;

[0122] The antioxidant agent is a mixture of HP136 and 1010 in a mass ratio of 1:1;

[0123] The anti-aging agent is a mixture of nano titanium dioxide in a mass ratio;

[0124] The metal soap has a mass ratio of aluminum stearate to zinc stearate = 1:3;

[0125] The dispersant is a mixture of sodium dodecylbenzene sulfonate, Tween 80 and polyoxyethylene hydrogenated castor oil in a mass ratio of 1:1:0.5.

[0126] The preparation method is as follows:

[0127] (1) adding carbon nanotube-modified epoxy resin, epoxy soybean oil and additives to 60% dispersant, and mixing at 70° C. until uniformly dispersed to obtain mixture 1;

[0128] (2) adding metal soap, anti-aging agent and antioxidant to the remaining dispersant, mixing and dispersing them uniformly at 65° C. to obtain mixture 2;

[0129] (3) Add mixture 1 to mixture 2 and mix at 350 rpm until the mixture is evenly dispersed.

[0130] Test 1

[0131] The stabilizers prepared in the above examples and comparative examples were added to chlorinated paraffin-70 at a volume ratio of 1:100, and after being mixed evenly, the thermal decomposition temperature (according to GB1680-8 standard), thermal stability time (first aging in a 175°C oven for 4 hours, then observed every 1 minute) and light stability (first aging in an ultraviolet lamp oven (55°C, 3rpm) for 4 hours, then observed every 5 minutes) were measured. The results are shown in Table 1.

[0132] Table 1

[0133] Group Thermal decomposition temperature / ℃ Thermal stability time / min Light stabilization time / min Example 1 239 72 323 Example 2 233 68 315 Example 3 228 67 318 Example 4 230 64 320 Comparative Example 1 179 53 294 Comparative Example 2 155 57 279 Comparative Example 3 201 45 290 Comparative Example 4 182 51 283 Comparative Example 5 197 56 266

[0134] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A composite stabilizer for chlorinated alkanes, It is characterized in that The raw materials of the stabilizer include the following components by weight: 15-25 parts of carbon nanotube modified epoxy resin, 15-25 parts of epoxidized soybean oil, 0.5-1 parts of metal soap, 5-10 parts of anti-aging agent, 1-5 parts of antioxidant, 1-5 parts of auxiliary agent and 30-60 parts of dispersant; The auxiliary agent is a mixture of sucrose ester and lecithin; The antioxidant is selected from one or more of HP136, 1010, and 168; The anti-aging agent comprises a mixture of nano silicon dioxide and nano titanium dioxide; The metal soap is selected from one or more of magnesium stearate, aluminum stearate, calcium stearate, and zinc stearate; The dispersant is selected from at least one of sodium lauryl sulfate, sodium dodecylbenzene sulfonate, dioctyl sodium sulfosuccinate, poloxamer 188, polyoxyethylene 400 monolaurate, polyoxyethylene hydrogenated castor oil, and polyoxyethylene nonylphenol ether.

2. The composite stabilizer according to claim 1, It is characterized in that The auxiliary agent is a mixture of sucrose ester and lecithin in a mass ratio of 1:3-5.

3. The composite stabilizer according to claim 1, It is characterized in that The anti-aging agent comprises a mixture of nano silicon dioxide and nano titanium dioxide in a mass ratio of 0.2-0.6:

1.

4. A method for preparing the composite stabilizer according to any one of claims 1 to 3, It is characterized in that The steps include: (1) adding carbon nanotube-modified epoxy resin, epoxy soybean oil and an auxiliary agent to a portion of the dispersant and mixing to obtain a mixture 1; (2) adding the metal soap, anti-aging agent and antioxidant to the remaining dispersant and mixing and dispersing them uniformly to obtain a mixture 2; (3) Add mixture 1 into mixture 2 and mix.

5. The preparation method according to claim 4, It is characterized in that The partial dispersant in step (1) is 60-75% dispersant; the mixing temperature is 70-90°C; and the mixing temperature in step (2) is 65-75°C.

6. Use of the composite stabilizer according to any one of claims 1 to 3 in the preparation of chlorinated alkanes for improving the stability.