阅读说明：本技术 一种苄泽疏水改性瓜尔胶增稠剂及其制备方法和应用 (Hydrophobic benzyl modified guar gum thickener and preparation method and application thereof ) 是由 苗霞 于 2019-10-12 设计创作，主要内容包括：本发明涉及油田压裂中使用的瓜尔胶衍生物技术领域的一种苄泽疏水改性瓜尔胶增稠剂及其制备方法。所述苄泽疏水改性瓜尔胶增稠剂,由包含以下组分的原料制备而成：a)瓜尔胶；b)苄泽缩水甘油醚；其中,所述苄泽缩水甘油醚与瓜尔胶的摩尔比为(0.5～2):1,优选(0.5～1):1,所述得到的苄泽疏水改性瓜尔胶增稠剂分子量与瓜尔胶分子量之比不小于0.1。此外,本发明还采用水/醇混合溶剂进行非均相悬浮反应的方法,所得苄泽疏水改性瓜尔胶增稠剂与单纯使用长疏水链段改性的瓜尔胶产品相比,增稠性能显著提高,具有良好应用前景。(The invention relates to a hydrophobic modified benzyl guar gum thickener and a preparation method thereof, belonging to the technical field of guar gum derivatives used in oilfield fracturing. The benzyl hydrophobic modified guar gum thickener is prepared from the following raw materials: a) guar gum; b) benzyl zeol glycidyl ether; wherein the molar ratio of the benzyl hydrophobic modified guar gum thickener to the guar gum is (0.5-2): 1, preferably (0.5-1): 1, and the ratio of the molecular weight of the obtained benzyl hydrophobic modified guar gum thickener to the molecular weight of the guar gum is not less than 0.1. In addition, the invention also adopts a method of carrying out heterogeneous suspension reaction by adopting a water/alcohol mixed solvent, and compared with a guar gum product modified by only using a long hydrophobic chain segment, the thickening performance of the obtained hydrophobic modified guar gum thickener is obviously improved, and the hydrophobic modified guar gum thickener has a good application prospect.)

1. A hydrophobic modified guar thickener of benzyl luster, characterized in that the hydrophobic modified guar thickener of benzyl luster is prepared from raw materials comprising the following components:

a) guar gum;

b) benzyl zelescent glycidyl ether;

wherein the molar ratio of the benzyl zerumour glycidyl ether to the guar gum is (0.5-2) to 1;

the ratio of the molecular weight of the obtained benzyl hydrophobic modified guar gum thickening agent to the molecular weight of guar gum is not less than 0.1.

2. The hydrophobically modified guar thickener according to claim 1, wherein:

the molar ratio of the benzyl zerumoid glycidyl ether to the guar gum is (0.5-1): 1.

The ratio of the molecular weight of the obtained benzyl hydrophobic modified guar gum thickening agent to the molecular weight of guar gum is not less than 0.5.

3. The hydrophobically modified guar thickener according to claim 1, wherein:

the benzyl zeer-type glycidyl ether is at least one selected from the group consisting of tetraethylene glycol monolauryl glycidyl ether, polyoxyethylene (10) hexadecyl glycidyl ether, polyoxyethylene (20) hexadecyl glycidyl ether, polyoxyethylene (2) octadecyl glycidyl ether, polyoxyethylene (2) hexadecyl glycidyl ether and polyoxyethylene (2) oleyl glycidyl ether.

4. The hydrophobically modified guar thickener according to claim 3, wherein:

the benzyl zeer-type glycidyl ether is at least one selected from polyoxyethylene (10) hexadecyl glycidyl ether and polyoxyethylene (20) hexadecyl glycidyl ether.

5. The hydrophobically modified guar thickener according to claim 1, wherein:

the preparation method of the benzylidene glycidyl ether comprises the following steps:

i) dissolving benzyl in anhydrous toluene, and removing water by azeotropy;

ii) under the protection of nitrogen, adding sodium hydride into the flask, wherein the molar ratio of the sodium hydride to the benzyl alcohol is (1:1) - (5:1), adding anhydrous toluene, dissolving the dehydrated benzyl alcohol in the anhydrous toluene again, adding the anhydrous toluene into the flask, and stirring for 1-3 hours;

iii) adding propylene oxide into the reactant, wherein the molar ratio of the propylene oxide to the benzyl is (2:1) - (7:1), and reacting for 5-8 h at 30-60 ℃;

iv) standing the reactant, separating solid from liquid, and distilling the liquid under reduced pressure to remove the solvent toluene to obtain the benzyl zeleside glycidyl ether.

6. A process for the preparation of hydrophobic modified guar thickener according to any of claims 1 to 5, characterized by the following steps:

1) stirring guar gum and a mixed solution of lower alcohol and water, introducing nitrogen, and slowly dropwise adding an inorganic alkali solution, wherein the mass of the added inorganic alkali accounts for 1-10% of that of the guar gum;

2) heating to 60-90 ℃, slowly adding benzyl zerumbet glycidyl ether dissolved in lower alcohol, and reacting for 4-12 hours, wherein the molar ratio of the benzyl zerumbet glycidyl ether to the guar gum is (0.5-2), and preferably (0.5-1): 1;

3) neutralizing the solution obtained in the step (2) to neutrality to obtain the hydrophobic modified guar gum thickening agent.

7. The method of preparing hydrophobic modified guar thickener according to claim 6, wherein:

in the step 1), the lower alcohol is selected from at least one of isopropanol, methanol, ethanol, n-propanol and allyl alcohol, preferably isopropanol; and/or the presence of a gas in the gas,

the content of the lower alcohol in the mixed solution is 70-90 wt%.

8. The method of preparing hydrophobic modified guar thickener according to claim 6, wherein:

in the step 1), the inorganic base is at least one selected from sodium hydroxide, potassium hydroxide and ammonium hydroxide; and/or the presence of a gas in the gas,

the concentration of the inorganic alkali solution is 0.01-52 wt%, preferably 30-50 wt%.

9. The method of preparing hydrophobic modified guar thickener according to claim 6, wherein:

in the step 1), the mass of the added inorganic base accounts for 2-5% of the mass of the guar gum.

10. Use of the hydrophobic modified guar thickener according to any of claims 1 to 5 in oil field fracturing.

Technical Field

The invention belongs to the technical field of guar gum derivatives used in organic synthetic chemistry and oil field fracturing, and particularly relates to a hydrophobic modified benzyl guar gum thickener as well as a preparation method and application thereof.

Background

Guar collagen powder has the defects of slow dissolution, more insoluble substances, difficulty in viscosity control, poor shearing resistance and the like, and guar gum derivatives with improved performance, such as hydroxypropyl guar gum, hydroxyethyl guar gum, carboxymethyl hydroxypropyl guar gum and the like, are usually obtained by chemical modification. In recent years, the hydrophobic association modification of guar gum becomes a research hotspot, and modification reagents can be divided into three types according to different grafting reaction functional groups: halogenated long alkanes, long chain alkenyl succinic anhydrides or long chain alkyl/alkenyl amides, long linear alkyl glycidyl ethers; these modifying agents react with guar or guar derivatives to graft hydrophobic long chain alkyl groups onto the primary-hydroxyl groups of the guar polysaccharide units. The brominated alkanes are generally adopted for hydrophobic modification in China, but the brominated alkanes have low reaction efficiency and high price. The long-chain alkenyl succinic anhydride or the long-chain alkyl/alkenyl amide is difficult to popularize and apply due to the complex introduction of groups. Alkyl glycidyl ethers are used abroad to modify polysaccharides, including guar gum.

Patent CN103554288A (instant guar gum and its preparation method) discloses an instant guar gum, which uses brominated long-chain alkane and guar gum suspended in a medium mainly comprising lower alcohol to perform hydrophobic modification of guar gum, to obtain a product with improved thickening performance, and has the disadvantage of low reaction efficiency of bromination reagent price.

Patent CN102827300A (a preparation method and application of a hydrophobically modified guar gum) discloses a preparation method of a hydrophobically modified guar gum, wherein guar gum is suspended in an ionic liquid and reacts with a hydrophobic alkyl long chain with a terminal group of carboxylic acid group under the catalysis of alkali to obtain the modified guar gum, the molecular weight of the product is large, and the water-soluble speed of the product is increased by the terminal group of carboxylic acid.

Patent US 4960876 (modided GALACTOMANNANS AND processes FOR the same PREPARATION) which grafts hydrophobic groups with a carbon chain length of 24 to 28 onto guar gum or derivatives thereof by etherification in a mixed solution of water AND isopropanol, in example 1 the product viscosity is increased by nearly three times compared to the original guar gum when the degree of substitution MS is 0.0032, but when the degree of substitution MS is 0.0091 the product viscosity is reduced from 4000 to 100 of the original guar gum, not only without increasing the thickening performance but also losing the thickening performance.

In the literature, "research on hydrophobization modification of guar" (coal and chemical industry, 2008(10): 24-26), bromohexadecane is used as a hydrophobic modification monomer to perform hydrophobization modification on natural guar to prepare hydrophobically associating guar, the influence of synthesis process conditions on the viscosity of the hydrophobically associating guar is researched, the reaction efficiency of a bromization reagent is low, and long chain consisting of simple hydrophobic groups easily causes the reduction of product solubility.

The literature "Flow properties of hydroxypropyl guar gum and its long-chain hydroxypropyl derivatives" (Carbohydrate Polymers,1995,28(3): 195-.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a hydrophobic modified guar gum thickener containing benzyl. In particular to a hydrophobic modified guar gum thickener which is obtained by using self-synthesized benzyl luster glycidyl ether to carry out hydrophobic modification on modified guar gum and a preparation method thereof.

One of the purposes of the invention is to provide a hydrophobic modified benzyl guar gum thickener which is prepared from the following raw materials:

a) guar gum;

b) benzyl zelescent glycidyl ether;

wherein the molar ratio of the benzyl zerumbet glycidyl ether to the guar gum is (0.5-2), preferably (0.5-1): 1.

The benzyl zeer-type glycidyl ether is selected from at least one of tetraethylene glycol monolauryl glycidyl ether, polyoxyethylene (10) hexadecyl glycidyl ether, polyoxyethylene (20) hexadecyl glycidyl ether, polyoxyethylene (2) octadecyl glycidyl ether, polyoxyethylene (2) hexadecyl glycidyl ether and polyoxyethylene (2) oleyl glycidyl ether; the benzylze-type glycidyl ether is preferably at least one selected from polyoxyethylene (10) hexadecyl glycidyl ether and polyoxyethylene (20) hexadecyl glycidyl ether.

The benzyl zeer glycidyl ether is synthesized autonomously, a hydrophilic chain segment (polyoxyethylene) of the benzyl zeer glycidyl ether can increase the solubility of a product, and the problem that the product is insoluble due to excessive grafting caused by excessively strong hydrophobicity of a long-chain alkane hydrophobic group is solved. The preparation method of the benzylzester-type glycidyl ether can be as described in the patent application No. 201610815855.9, which is incorporated herein in its entirety into the patent application No. 201610815855.9.

The preparation method of the benzyl zeer glycidyl ether comprises the following steps:

i) dissolving benzyl in anhydrous toluene, and removing water by azeotropy; the dosage ratio of the benzyl luster to the anhydrous toluene can be 1g of benzyl luster dissolved in 5-20 mL of anhydrous toluene;

ii) adding sodium hydride into the flask under the protection of nitrogen, wherein the molar ratio of the sodium hydride to the benzyl is (1:1) - (5:1), and then adding anhydrous toluene; then, dissolving the dehydrated benzyl resin in anhydrous toluene again, adding the anhydrous toluene into a flask, and stirring for 1-3 hours; in the step 2), the dosage proportion of the anhydrous toluene is 1g of unboiled benzyl luster corresponding to 3-10 mL of anhydrous toluene;

iii) adding propylene oxide into the reactant, wherein the molar ratio of the propylene oxide to the benzyl is (2:1) - (7:1), and reacting for 5-8 h at 30-60 ℃;

iv) standing the reactant, separating solid from liquid, and distilling the liquid under reduced pressure to remove the solvent to obtain the benzylzelesin glycidyl ether.

Another object of the present invention is to provide a method for preparing the hydrophobic modified guar gum thickener, comprising the steps of:

1) stirring guar gum and a mixed solution of lower alcohol and water, introducing nitrogen, and slowly dropwise adding an inorganic alkali solution, wherein the mass of the added inorganic alkali accounts for 1-10% of that of the guar gum;

2) heating to 60-90 ℃, slowly adding benzyl zerumer glycidyl ether dissolved in lower alcohol, and reacting for 4-12 hours, wherein the molar ratio of the benzyl zerumer glycidyl ether to the guar gum is (0.5-2): 1;

3) neutralizing the solution obtained in the step (2) to neutrality to obtain the hydrophobic modified guar gum thickening agent.

Wherein, in the step 1), the inorganic base includes but is not limited to at least one of sodium hydroxide, potassium hydroxide and ammonium hydroxide.

The concentration of the inorganic alkali solution is 0.01-52 wt%, preferably 30-50 wt%.

In the step 1), preferably, the mass of the added inorganic base accounts for 2-5% of the mass of the guar gum.

In the step 1), the lower alcohol includes but is not limited to at least one of isopropanol, methanol, ethanol, n-propanol and allyl alcohol, preferably isopropanol.

In the step 1), the content of the lower alcohol in the mixed solution is 70-90 wt%.

In the step 2), the molar ratio of the benzyl zerumbet-type glycidyl ether to the guar gum is preferably (0.5-1): 1.

In the step 3), the neutralization step further comprises the steps of filtering, washing, drying and the like, which are all common methods.

Specifically, the preparation method can specifically adopt the following technical scheme:

adding guar gum and mixed solution of appropriate amount of lower alcohol and water into a three-necked bottle, stirring, and introducing nitrogen for 30 min; slowly dropwise adding an inorganic alkali solution accounting for 1-10% of the mass of the guar gum; heating to the reaction temperature of 60-90 ℃, slowly adding benzyl glycidyl ether dissolved in lower alcohol, and reacting for 4-12 hours; neutralizing with dilute hydrochloric acid to neutrality, pouring out all reactants, filtering, stirring and washing with a mixture of 80% and 90% ethanol and water in sequence, filtering, stirring and washing with absolute ethanol, filtering, removing unreacted residual reactants such as benzyl glycidyl ether and the like, and finally drying in a vacuum oven at 60 ℃ for 12 hours to obtain a white powder product.

The invention also aims to provide the application of the benzyl hydrophobic modified guar gum thickener in oilfield fracturing.

The invention adopts the suspension reaction in the mixed solvent of lower alcohol and water to realize the modification, such as: mixtures of isopropanol, methanol, ethanol, ethylene glycol, and the like with water. In the conventional reaction, the reactants can only react at the interface of two phases, so that the reaction efficiency is not high. However, the guar gum is modified by adopting the benzyl glycidyl ether which is autonomously synthesized and simultaneously has the hydrophilic chain segment and the hydrophobic chain segment, and the hydrophilic chain segment increases the water solubility of the product, so that compared with the prior art in which the hydrophobic chain segment with the same length is simply used for modification, the modified guar gum has better water solubility and thickening performance.

The invention has the following effects:

first, the present invention employs autonomously synthesized benzyl zest glycidyl ether as a modifying monomer, including polyoxyethylene (10) cetyl glycidyl ether, polyoxyethylene (20) cetyl glycidyl ether, etc., and the preparation method thereof is mentioned in the patent application No. 201610815855.9. The monomer contains a hydrophilic chain segment and a hydrophobic chain segment, the hydrophilic chain segment (polyoxyethylene) can increase the solubility of the product, and the defect that long-chain alkane is only used as a hydrophobic group in the prior invention is overcome: in the prior art, only long-chain alkane is used as a hydrophobic group, the hydrophobicity of the long-chain alkane hydrophobic group is too strong, the proper grafting ratio range is narrow, if the grafting ratio is too low, the hydrophobic group cannot form a three-dimensional network structure, the hydrophobic association effect cannot be achieved, the thickening effect achieved by the hydrophobic association cannot be achieved, and if the grafting ratio is too high, the product is insoluble, and deviates from the original purpose of hydrophobic modification thickening, so that a mature product of the long-chain alkane hydrophobic modified guar gum is not available up to now.

Secondly, the invention adopts the autonomously synthesized benzyl zest glycidyl ether as the modified monomer, and compared with the glycidyl ether adopting the alkyl chain with the same length, the modified product has better thickening performance.

Thirdly, the invention adopts glycidyl ether as a reactive group, the glycidyl ether is grafted on the hydroxyl of the guar gum sugar unit through the open loop of the terminal epoxy ring, compared with the halohydrocarbon commonly adopted in the domestic prior patent, the reaction activity is higher, the reaction efficiency is improved, and the further reaction can be prevented.

Fourthly, the method of carrying out heterogeneous suspension reaction in a water/alcohol mixed solvent is adopted, and although guar gum degradation is possible due to the fact that reaction temperature is high (60-90 ℃) and strong inorganic base (usually NaOH) is used as a catalyst, experiments prove that the hydrophobically modified guar gum product prepared by the method can still keep relatively large molecular weight and the thickening performance of the product is remarkably improved.

The invention has important reference significance for chemical modification, especially hydrophobic modification of guar gum and application of guar gum in oilfield exploitation.

Drawings

FIG. 1 is a graph of viscosity as a function of shear rate for a sample 1 (polyoxyethylene (20) cetyl glycidyl ether hydrophobically modified guar) solution at a concentration of 4.8g/L and for the same concentration guar and a comparative sample 1 (cetyl straight hydrophobically modified guar) solution at 25 ℃.

Open symbols: increasing the shear rate to obtain a curve; closed symbols: curve obtained by decreasing the shear rate.

FIG. 2 is a graph showing the change in storage modulus and loss modulus with frequency at 25 ℃ for a 4.8g/L concentration solution of sample 2 in pure water and 0.1M sodium chloride solution at 25 ℃.

Detailed Description

While the present invention will be described in detail with reference to the following examples, it should be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the present invention.

The starting materials used in the embodiments of the present invention are commercially available.

The invention adopts a TA AR2000 viscometer to test viscosity. The method comprises the steps of dissolving a sample in water or 0.1M NaCl solution at room temperature, stirring for 12 hours to prepare a solution with a certain concentration, placing the solution into a refrigerator, standing for 12 hours, and testing by using a American TA AR2000 viscometer.

The invention uses gel chromatography to measure the molecular weight, and the mobile phase is 100mM phosphate buffer solution; the flow rate is 0.8 mL/min; the column temperature is 25 ℃; the sample injection amount is 500-1500 uL; the detection wavelength is 280 nm.

Example 1

0.0089mol (5.89g) of polyoxyethylene (10) hexadecyl ether was dissolved in anhydrous toluene, and azeotropic removal of water was carried out. Under the protection of nitrogen, 0.044mol (1.05g) of sodium hydride is added into a flask, 58mL of anhydrous toluene is added, then the dehydrated benzyl is dissolved in 30mL of anhydrous toluene again, the obtained solution is added into the flask, and the obtained mixture is stirred for 1 hour. 0.0623mol (3.60g) of propylene oxide were added to the reaction mixture and reacted at 30 ℃ for 5 hours. The reaction mixture was placed in a refrigerator at 4 ℃ overnight to allow solid-liquid separation. The liquid was carefully separated and toluene was distilled off under reduced pressure to give polyoxyethylene (20) hexadecylglycidyl ether (code56-EPOXIDE)。

Adding a mixed solution of 50g of guar gum (MS is 2.5) and 500g of isopropanol (70 mass percent content) and water into a 1000ml three-necked bottle, stirring, and introducing nitrogen for 30 min; slowly dripping 5g of 48 percent sodium hydroxide solution; heating to 60 ℃, slowly adding polyoxyethylene (20) hexadecyl glycidyl ether dissolved in a proper amount of isopropanol, wherein the molar ratio of the polyoxyethylene (20) hexadecyl glycidyl ether to the guar gum is 0.55:1, and reacting for 12 hours; neutralizing with dilute hydrochloric acid to neutrality, pouring out all reactants, filtering, sequentially washing with 80% and 90% acetone and water mixture under stirring, filtering, washing with acetone under stirring, filtering, and collecting unreactedResidual reactants such as 56-EPOXIDE were removed and finally dried in a vacuum oven at 60 deg.C for 12h to give product sample 1 as a white powder (G-Brij 56E). Wherein, the molecular weight of sample 1 is 110.5 ten thousand.

Example 2

Polyoxyethylene (20) hexadecyl glycidyl ether was prepared in the same manner as in example 1.

A mixed solution of 50g of guar gum (MS 2.5) and 500g of isopropanol (90% by mass content) in water was put into a 1000ml three-necked flask, stirred, and introducedNitrogen for 30 min; slowly dropwise adding 3g of 48% sodium hydroxide solution; heating to 90 ℃, slowly adding polyoxyethylene (20) hexadecyl glycidyl ether dissolved in a proper amount of isopropanol, wherein the molar ratio of the polyoxyethylene (20) hexadecyl glycidyl ether to the guar gum is 0.6:1, and reacting for 4 hours; neutralizing with dilute hydrochloric acid to neutrality, pouring out all reactants, filtering, sequentially washing with 80% and 90% acetone and water mixture under stirring, filtering, washing with acetone under stirring, filtering, and collecting unreactedResidual reactants such as 56-EPOXIDE were removed and finally dried in a vacuum oven at 60 deg.C for 12h to provide product sample 2 as a white powder. Sample 2, among others, had a molecular weight of 104.9 ten thousand.

In general, the addition of NaCl has a strong effect on the solution viscosity values of the modified guar samples, and FIG. 2 is a plot of the storage modulus and loss modulus as a function of frequency for a 4.8g/L concentration of sample 2 in pure water at 25 ℃ and 0.1M sodium chloride solution. It can be seen that the addition of NaCl at a concentration of 0.1M results in a strong reduction in the storage and loss moduli G 'and G', respectively. It can be concluded from this that the salt promotes hydrophobic interactions, resulting in strong aggregation of the modified guar in aqueous solution.

Example 3

Polyoxyethylene (20) hexadecyl glycidyl ether was prepared in the same manner as in example 1.

Adding a mixed solution of 50g of guar gum (MS is 2.5) and 500g of isopropanol (90 mass percent content) and water into a 1000ml three-necked bottle, stirring, and introducing nitrogen for 30 min; slowly dropwise adding 3g of 48% sodium hydroxide solution; heating to 90 ℃, slowly adding polyoxyethylene (20) hexadecyl glycidyl ether dissolved in a proper amount of isopropanol, wherein the molar ratio of the polyoxyethylene (20) hexadecyl glycidyl ether to the guar gum is 1:1, and reacting for 4 hours; neutralizing with dilute hydrochloric acid to neutrality, pouring out all reactants, filtering, sequentially washing with 80% and 90% acetone and water mixture under stirring, filtering, washing with acetone under stirring, filtering, and collecting unreactedResidual reactants such as 56-EPOXIDE were removed and finally dried in a vacuum oven at 60 deg.C for 12h to provide product sample 3 as a white powder. Of these, sample 3 had a molecular weight of 97.2 ten thousand.

Comparative example 1

Comparative sample 1(G-GHE) was prepared using the same procedure as in example 1, wherein the benzylzester type glycidyl ether was replaced with hexadecyl glycidyl ether.

Sample 1(G-Brij6E), comparative sample 1(G-GHE) and unmodified Guar gum stock (Guar) were each formulated to a concentration of 4.8G/L, comparing the viscosity of the three solutions as a function of shear rate, and the results are shown in FIG. 1. As can be seen from figure 1, the viscosity of both the sample 1 solution and the comparative sample 1 solution is higher than that of the unmodified guar solution at the same concentration, whereas the sample 1 solution has the highest viscosity, indicating that the guar modified with the brij glycidyl ether of the present invention has the most significant thickening effect. It can be seen that, in the hydrophobic modification reaction of guar gum, in the case of the same hydrophobic segment (both the hydrophobic segments of sample 1 and comparative sample 1 are hexadecyl), the addition of the hydrophilic segment (polyoxyethylene group) is beneficial to the thickening performance of the product. In addition, when the water solubility of sample 1 and comparative sample 1 were compared and prepared as solutions of 25g/L, respectively, sample 1 was completely dissolved and comparative sample 1 was precipitated by a small amount, indicating that sample 1 had better water solubility than comparative sample 1.

Comparative example 2

Using the preparation method of patent 201710839079.0 as comparative example 2, using the same molar ratio of benzylzeo-type glycidyl ether to guar as in example 1, comparative sample 2(G-BrijE2) was prepared. The molecular weight of each sample was measured using gel chromatography and the results are shown in table 1 below. It can be seen that guar gum is severely degraded when the preparation method of patent 201710839079.0 is used, whereas guar gum is not severely degraded when the preparation method of the present invention is used.

TABLE 1 molecular weights of guar, sample 1 and comparative sample 2

Sample (I)	Guar gum	Sample 1	Comparative sample 2
				Molecular weight (ten thousand)	162.8	110.5	8.1

Comparative example 3

Using the same procedure as in example 2, comparative sample 3(G-BrijE3) was prepared except that the molar ratio of the benzylzester-type glycidyl ether to guar was changed to 0.4: 1. The viscosities of sample 2 and comparative sample 3 were measured separately using a TA AR2000 viscometer, with the viscosity of sample 2 being significantly higher than comparative sample 3.