Polyglycerin

Abstract

To provide a manufacturing method for a polyglycerin with excellent productivity and controlled branch structures.SOLUTION: A manufacturing method for a polyglycerin according to the present invention is characterized by reacting a (poly)glycerin and a (poly)glycerin (poly)glycidyl ether. A polyglycerin according to the present invention is characterized by having a weight-average molecular weight of 300-25,000 and a branching degree of 0.1-0.6.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to polyglycerol. [Background technology]

[0002] Polyglycerol is used as a raw material in the production of various chemical products such as moisturizers, thickeners, plasticizers, and monomers. The properties of polyglycerol in these applications vary depending on the degree of polymerization and branching structure. Therefore, it is necessary to adjust the degree of polymerization and branching structure as needed depending on the intended use.

[0003] Conventional methods for producing polyglycerol are generally carried out industrially by high-temperature dehydration polymerization of glycerol using an alkali catalyst and ring-opening polymerization of glycidol. Polyglycerol produced by the high-temperature dehydration condensation method has a degree of polymerization of about 2 to 10 and a linear structure with little branching. On the other hand, polyglycerol produced by the ring-opening polymerization of glycidol has a degree of polymerization of about 4 to 40 and a highly branched structure. In other words, the high-temperature dehydration condensation reaction results in a low molecular weight and low branching, while the ring-opening polymerization of glycidol results in a highly branched structure regardless of molecular weight. Therefore, it is difficult to simultaneously control the molecular weight and the degree of branching with conventional production methods.

[0004] In particular, to obtain a high-molecular-weight polyglycerol, either a polyglycerol having a linear structure or a polyglycerol having a high degree of branching obtained by polymerization of glycidol is required. It is difficult to obtain a polyglycerol having a high molecular weight and a controlled degree of branching. Since the properties of polyglycerol vary greatly depending on its molecular weight and degree of branching, it is desirable to control these and produce a wide variety of polyglycerols that can be used for many purposes.

[0005] Patent Document 1 describes a method for producing polyglycerol using glycidol whose hydroxyl groups are protected with benzyl groups. However, the polyglycerol produced by this method is essentially a linear polyglycerol having an ether bond derived from a hydroxyl group at one end of glycerol and a secondary hydroxyl group at the center, and it is not possible to obtain a polyglycerol with a highly branched structure, so this does not provide a fundamental solution. In addition, controlling the structure of polyglycerol using such protecting groups increases the number of production steps, such as protection and deprotection, which results in problems such as reduced productivity and increased costs.

[0006] Patent Document 2 describes a method for producing a crosslinked polyglycerol by reacting a polyglycerol with glycerol diglycidyl ether. However, this method uses a branched polyglycerol as a raw material. Therefore, the obtained polyglycerol depends on the structure of the polyglycerol used as a raw material, and the structure of the obtained polyglycerol is limited, making it impossible to obtain a polyglycerol with an arbitrary branching degree or molecular weight.

[0007] Patent Document 3 describes highly branched, high-molecular-weight polyglycerols and polyglycidols. However, because these are produced by polymerization of glycidol, they tend to be highly branched, and the degree of branching and molecular weight cannot be adjusted arbitrarily. In addition, dichloromethane is used as a solvent, which increases the environmental load and the cost of ensuring the safety of the working environment. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 09-235246 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-74048 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-215734 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a method for producing polyglycerol that makes it possible to adjust the molecular weight and degree of branching and thereby to produce a wider variety of polyglycerols with good productivity. [Means for solving the problem]

[0010] The present inventors have found that polyglycerol can be synthesized while controlling the molecular weight and degree of branching by reacting (poly)glycerol with (poly)glycerol (poly)glycidyl ether, and have thus completed the present invention. In this specification, "(poly)glycerin" means "glycerin" and / or "polyglycerin." In addition, in this specification, the term "(poly)glycidyl ether" means "glycidyl ether" and / or "polyglycidyl ether".

[0011] The present invention is a polyglycerol characterized by having a weight-average molecular weight of 300 to 25,000 and a degree of branching of 0.1 to 0.6. The polyglycerol preferably has a dispersity of 3 or more. The polyglycerol preferably has a ratio of primary hydroxyl groups to secondary hydroxyl groups of 30 / 70 to 50 / 50. [Effects of the Invention]

[0012] The present invention is a method for producing polyglycerol by reacting (poly)glycerol with a (poly)glycerol-based epoxy group, which is characterized by being able to adjust the molecular weight and degree of branching without introducing a protecting group into the raw material. In particular, it is possible to suitably obtain polyglycerol having a high molecular weight and a degree of branching controlled within a suitable range. Furthermore, the method is also effective in that it allows the production of a desired polyglycerol without reducing productivity or increasing costs due to an increase in the number of production steps such as the introduction and deprotection of protecting groups. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 shows an example of a 13C-NMR spectrum for calculating the degree of branching and the abundance ratio of primary hydroxyl groups to secondary hydroxyl groups in the polyglycerol of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The method for producing polyglycerol of the present invention involves the reaction of (poly)glycerol with (poly)glycerol (poly)glycidyl ether. Furthermore, the reaction proceeds by inducing a reaction between a hydroxyl group and an epoxy group. It is more preferable to select reaction conditions that do not result in the formation of an ether bond due to a hydroxyl-hydroxyl group reaction. This results in one end of the reaction occurring in the epoxy ring of the (poly)glycerol (poly)glycidyl ether. This method is therefore advantageous in that the degree of polymerization and degree of branching of the resulting polyglycerol can be adjusted by adjusting the degree of polymerization of the (poly)glycerol used, the degree of polymerization of the (poly)glycerol (poly)glycidyl ether, and the degree of glycidyl group introduction, as well as by adjusting the amounts of each component.

[0015] That is, when a (poly)glycerin having a low degree of polymerization is used and the proportion of (poly)glycerin (poly)glycidyl ether used is increased, a polyglycerin with a high degree of branching is easily obtained, and when the opposite selection of raw materials is performed (using a (poly)glycerin having a high degree of polymerization and reducing the proportion of (poly)glycerin (poly)glycidyl ether used), a polyglycerin with a low degree of branching can be obtained.

[0016] The (poly)glycerin used as a raw material in the present invention is preferably a (poly)glycerin having an average degree of polymerization calculated from the hydroxyl value of 1 to 20, more preferably an average degree of polymerization of 2 to 15. Polyglycerins having an average degree of polymerization within the above range can be obtained as those having a linear structure.

[0017] Furthermore, when the (poly)glycerin has an average degree of polymerization of 3 or more, it is preferably linear. As described above, in the present invention, it is important to control the degree of branching of the polyglycerin in the final product. Therefore, it is preferable to use a (poly)glycerin with a linear structure in order to control the degree of branching. In the present invention, the linear structure refers to one in which L13 is 0, or the value of L14 / L13 is 2 or more, and the proportion of D is 5% or less, as measured by the following method.

[0018] Specific examples of (poly)glycerin include glycerin, diglycerin, triglycerin, tetraglycerin, hexaglycerin, and decaglycerin. Commercially available products that can be used include glycerin, diglycerin S, R-PG, polyglycerin #310, polyglycerin #500, and polyglycerin #750 (all manufactured by Sakamoto Pharmaceutical Industry Co., Ltd.).

[0019] Here, the average degree of polymerization is the average degree of polymerization (n) of polyglycerol calculated from the hydroxyl value by terminal group analysis. Specifically, the average degree of polymerization is calculated from the following formulas (Formula 1) and (Formula 2). (Formula 1) Molecular weight=74n+18 (Equation 2) Hydroxyl value = 56110(n+2) / molecular weight The hydroxyl value in the above formula (2) is a numerical value that indicates the number of hydroxyl groups contained in polyglycerol, and refers to the number of milligrams of potassium hydroxide required to neutralize the acetic acid required to acetylate the free hydroxyl groups contained in 1 g of polyglycerol. The number of milligrams of potassium hydroxide is calculated in accordance with "Standard Test Methods for the Analysis of Fats, Oils and Related Materials, 2013 Edition, Established by the Japan Oil Chemists' Society," edited by the Japan Oil Chemists' Society.

[0020] The (poly)glycerin (poly)glycidyl ether used as a raw material in the present invention is a compound in which one or more hydroxyl groups in (poly)glycerin have been substituted with a glycidyl ether group. The method for producing polyglycerin of the present invention is a method for obtaining a high-molecular-weight polyglycerin by ring-opening of the epoxy groups in the glycidyl groups and reaction with the hydroxyl groups. The degree of branching can be controlled by utilizing the reaction of the epoxy groups in the (poly)glycerin (poly)glycidyl ether.

[0021] The (poly)glycerin that is the basis of the (poly)glycerin (poly)glycidyl ether is preferably a (poly)glycerin having an average degree of polymerization calculated from the hydroxyl value of 1 to 20, more preferably an average degree of polymerization of 2 to 15. When the average degree of polymerization is within the above range, it becomes easy to control the reaction with the (poly)glycerin.

[0022] When the number of repeating units in the glycerin skeleton of the (poly)glycerin (poly)glycidyl ether is 3 or more, the (poly)glycerin is preferably a linear polyglycerin similar to the (poly)glycerin. This is preferable because the structure of the resulting polyglycerin can be suitably controlled by using a compound obtained by (poly)glycidyl etherifying such a (poly)glycerin. The term "linear" in (poly)glycerin is the same as that in the raw material (poly)glycerin described above.

[0023] Specific examples of (poly)glycerin (poly)glycidyl ethers include, but are not limited to, glycerin (poly)glycidyl ether, diglycerin (poly)glycidyl ether, tetraglycerin (poly)glycidyl ether, hexaglycerin (poly)glycidyl ether, decaglycerin (poly)glycidyl ether, etc. Furthermore, mixtures of two or more of these may be used as raw materials.

[0024] The (poly)glycerin (poly)glycidyl ether preferably has an average of 1 to 22 glycidyl groups per molecule. The lower limit of the number of glycidyl groups is more preferably 2, while the upper limit of the number of glycidyl groups is more preferably 8. When the number of glycidyl groups is within the above range, the reactivity is good and control is easy.

[0025] The (poly)glycerin (poly)glycidyl ether preferably has an epoxy equivalent of 120 to 200. The lower limit of the epoxy equivalent is more preferably 130, while the upper limit of the epoxy equivalent is more preferably 195. When the epoxy equivalent is within the above range, polymerization between the (poly)glycerin (poly)glycidyl ethers is suppressed, and polymerization with the (poly)glycerin proceeds favorably.

[0026] Furthermore, the (poly)glycerin (poly)glycidyl ether may be a mixture of two or more compounds. In particular, when a polyglycerin having low uniformity and high dispersity is required, compounds having various degrees of polymerization, numbers of glycidyl groups, and epoxy equivalents may be used in combination.

[0027] The (poly)glycerin (poly)glycidyl ether can be easily produced by a conventionally known method, such as a method of reacting (poly)glycerin with epichlorohydrin in the presence of a Lewis acid in a solvent such as toluene, followed by epoxidation with an alkali metal hydroxide.

[0028] As for the combination of the (poly)glycerin and (poly)glycerin (poly)glycidyl ether, the use of a low-molecular-weight (poly)glycerin tends to increase the degree of branching, while the use of a high-molecular-weight (poly)glycerin tends to decrease the degree of branching. In addition, when a low molecular weight (poly)glycerin (poly)glycidyl ether is used, the degree of branching tends to be high, and when a high molecular weight (poly)glycerin (poly)glycidyl ether is used, the degree of branching tends to be low.

[0029] In the method for producing a polyglycerol of the present invention, it is preferable to set reaction conditions such that the epoxy groups of the (poly)glycerol (poly)glycidyl ether undergo ring-opening and react with the hydroxyl groups of the (poly)glycerol to form a polyglycerol. That is, it is more preferable to set reaction conditions such that a side reaction, such as a reaction between hydroxyl groups to form an ether bond, does not occur. This is because the formation of branches due to such a reaction makes it difficult to control the structure of the polyglycerol product, which is the objective of the present invention.

[0030] The compounding ratio of the (poly)glycerin and the (poly)glycerin (poly)glycidyl ether may be set as appropriate. For example, it is preferable to react 0.05 to 2 times by weight of the (poly)glycerin (poly)glycidyl ether with the (poly)glycerin.

[0031] The catalyst used in the present invention may be an acid catalyst or an alkali catalyst, but from the viewpoint of suppressing side reactions, an alkali catalyst is preferred, and alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, cesium hydroxide, etc. are more preferred. The amount of these alkali metal hydroxides used is preferably 0.1 to 0.5 wt % based on the total amount of (poly)glycerin and (poly)glycerin (poly)glycidyl ether.

[0032] The reaction temperature between (poly)glycerin and (poly)glycerin (poly)glycidyl ether is preferably 120° C. to 180° C., more preferably 140° C. to 160° C. If the reaction temperature is lower than 120° C., the reaction rate may be significantly slow, whereas if the reaction temperature exceeds 180° C., the product may be discolored, an odor may be generated, and problems such as a side reaction, etherification reaction between hydroxyl groups, may proceed, may occur.

[0033] In the production method of the present invention, the reaction between (poly)glycerol and (poly)glycerol (poly)glycidyl ether can be carried out even in the absence of a solvent, and therefore the production method of the present invention is useful in that it is safe, allows polyglycerol to be produced easily, and does not impose a burden on the environment.

[0034] Furthermore, the reaction between (poly)glycerin and (poly)glycerin (poly)glycidyl ether may be carried out in the presence of 5 to 20 wt % of an aprotic polar solvent, if necessary. The aprotic polar solvent is not particularly limited, but polyethylene glycol alkyl ethers are preferred, and specific examples include diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, and pentaethylene glycol diethyl ether. Among these, diethylene glycol dimethyl ether and triethylene glycol dimethyl ether are more preferred from the viewpoints of their boiling points being equal to or higher than the reaction temperature and being easily removed by distillation after polymerization.

[0035] When reacting (poly)glycerin with (poly)glycerin (poly)glycidyl ether, a method in which the (poly)glycerin (poly)glycidyl ether is added to the (poly)glycerin and the two are reacted is preferred. The (poly)glycerin (poly)glycidyl ether is preferably added dropwise gradually, and the rate of addition should be set so that the entire amount is added dropwise over 30 to 60 minutes. In particular, if the addition is performed faster than 30 minutes, a large amount of unreacted glycidyl ether remains in the reaction system, and the glycidyl ethers tend to react with each other. After the end of the addition, the reaction should be continued for 5 to 10 hours, preferably 6 to 8 hours. If the reaction time is shorter than 5 hours, epoxy groups are likely to remain in the polyglycerin skeleton, while if the reaction time exceeds 10 hours, problems such as discoloration of the product and odor generation may occur.

[0036] The polyglycerol obtained may be further purified by distilling off low molecular weight compounds under reduced pressure or by blowing saturated heated steam into the polyglycerol, or by treating the polyglycerol with activated carbon, ion exchange resin, an adsorbent, or the like, or by reprecipitation. The polyglycerol of the present invention may contain chlorine components derived from the raw materials used, or may be one from which chlorine components have been removed by purification or the like, as necessary.

[0037] The present invention also relates to polyglycerols having specific chemical structures, which are structures that can be obtained by the method for producing polyglycerols of the present invention.

[0038] The polyglycerol of the present invention preferably has a weight-average molecular weight (Mw) in the range of 300 to 25,000. The lower limit is more preferably 500, even more preferably 1,000, particularly preferably 1,300, and most preferably 3,600. The upper limit is more preferably 22,000, even more preferably 20,000. When the upper limit of the weight-average molecular weight is in the above range, excellent handleability is achieved. Furthermore, when the lower limit is in the above range, a polyglycerol with high dispersity can be obtained.

[0039] Also, the dispersity (Mw / Mn) is preferably 3 to 90. In particular, when the average molecular weight is the same, it is thought that a polymer with a high dispersity (wide molecular weight distribution) can more easily obtain the molecular weight effect in interfacial adsorption than a polymer with a monodisperse (narrow molecular weight distribution), thereby enhancing the interfacial interaction.

[0040] In the production method of the present invention, it is also possible to control the degree of polydispersity. That is, polyglycerols having a wide molecular weight distribution and polyglycerols having a narrow molecular weight distribution can be appropriately produced depending on the purpose. Furthermore, the production method of the present invention makes it possible to produce polyglycerols having a degree of polydispersity that has not been possible to produce in the past.

[0041] The weight average molecular weight (Mw) and number average molecular weight (Mn) are values measured by GFC analysis using polyethylene glycol / polyethylene oxide as a standard sample with the following apparatus and conditions. Separation column: SB-806M (8 mm x 30 mm, Shodex) Column temperature: 40℃ Mobile phase solvent: ion-exchanged water Mobile phase flow rate: 1.0 mL / min Sample concentration: 0.5 wt% Injection volume: 50μL Detector: RI detector (Waters2414, Waters)

[0042] Furthermore, in consideration of the difficulty of production, the polyglycerol of the present invention preferably has a degree of branching (DB) within the range of 0.1 to 0.6.

[0043] The method for producing a polyglycerol of the present invention also makes it possible to control the degree of branching. This method is also preferred in that it is possible to suitably obtain a polyglycerol with a controlled degree of branching, even if the molecular weight is high as described above. Since the degree of branching affects the physical properties of the polyglycerol, such as polarity and viscosity, this method is preferred in that it can be controlled within the above-mentioned specific range simply by selecting the raw materials used.

[0044] The lower limit of the degree of branching is more preferably 0.15, and even more preferably 0.2, and the upper limit of the degree of branching is more preferably 0.55, and even more preferably 0.4. The higher the degree of branching, the higher the hydrophilicity. If the degree of branching is within the above range, a highly hydrophilic polymer can be obtained even if it has a small molecular weight.

[0045] The production method of the present invention can produce a polyglycerol having a high weight-average molecular weight while controlling the degree of branching, and the weight-average molecular weight is preferably 300 to 25,000 and the degree of branching is preferably 0.1 to 0.6, and more preferably 3,600 to 25,000 and the degree of branching is 0.15 to 0.4.

[0046] The degree of branching was measured using the following equipment and conditions: 13 The value was calculated by C-NMR. Measurement conditions: Polyglycerol was dissolved in deuterated methanol to a concentration of 10 wt %. Equipment used: 175MHz 13C-NMR (Bruker AVANCE700) Measurement conditions: Quantitative measurement mode, pulse interval 10 seconds

[0047] Please see below for details. 13 Structural analysis of polyglycerol by C-NMR was carried out based on the method described in "Controlled Synthesis of Hyperbranched polyglycerols by Ring-Opening Multibranching Polymerization," Macromoleculers 1990, 32, 4240-4246.

[0048] The glycerin present in polyglycerol can be classified into the following five structures based on the bonding pattern between its hydroxyl group and ether bond.

[0049] [ka]

[0050] Polyglycerin 13 When C-NMR measurements are performed, carbon is divided into several peaks based on its chemical environment. 13 An example of the C-NMR measurement results is shown in Figure 1. Eight peaks, A to H, are observed. These peaks are identified to carbon atoms at specific positions in the above-mentioned L13, D, L14, T1, and T2 structures, respectively. Therefore, the amounts of the L13, D, L14, T1, and T2 structures can be calculated based on the integral ratio of each peak.

[0051] Specifically, the abundance ratio of each of the structures L13, D, L14, T1, and T2 represented by the above general formula can be calculated using the integral ratio of each peak (IntA, etc.) and the following formula. L13=IntB D=IntC L14=(IntD / 2+IntF-L13) / 2 T1=(IntG+(IntE-2D) / 2) / 2 T2=(IntG+(IntE-2D) / 2) / 2

[0052] The degree of branching (DB) is calculated from the abundance ratios of D, L13, and L14 using the following formula: Branching degree (DB)=2D / (2D+L13+L14)

[0053] In the polyglycerol of the present invention, the ratio of primary hydroxyl groups to secondary hydroxyl groups is preferably 30 / 70 to 50 / 50, and more preferably 30 / 70 to 45 / 55. Thus, it is speculated that polyglycerols with a relatively large number of secondary hydroxyl groups have a high metal ion capturing ability, particularly due to the secondary hydroxyl groups present inside the polyglycerol. The production method of the present invention is also preferable in that the above ratio can be appropriately controlled.

[0054] The ratio of primary hydroxyl groups to secondary hydroxyl groups is 13 This value was calculated from the abundance ratios of L13, L14, D, T1, and T2 calculated in the C-NMR spectrum and the number of primary and secondary hydroxyl groups bonded to each. The number of primary hydroxyl groups and secondary hydroxyl groups in each of the above structural units is as shown in Table 1.

[0055] [Table 1]

[0056] Referring to Table 1 above, the abundance ratio of each hydroxyl group can be calculated using the following formula by multiplying the abundance ratio of each structure in polyglycerol by the number of each hydroxyl group and adding up the results. Primary hydroxyl group: (L13×1) + (T1×1) + (T2×2) Secondary hydroxyl group: (L14 × 1) + (T1 × 1) The ratio of the proportions of primary hydroxyl groups to secondary hydroxyl groups calculated by the above formula is converted into a percentage, which is the abundance ratio of primary hydroxyl groups to secondary hydroxyl groups.

[0057] The resulting polyglycerol can be used in various applications as a dispersant or resin raw material. It can also be used as a resin raw material after, for example, being converted into an acrylic ester, epoxidized, urethane-modified, allyl etherified, or alkoxysilylated by reaction of the hydroxyl group. Furthermore, it can be used as a dispersant for metal oxide fine particles, for example.

[0058] In the polyglycerol of the present invention, a portion of the hydroxyl groups can be converted to epoxy groups by a known method. The polyglycerol of the present invention can also be acrylated by reacting a portion of the hydroxyl groups with (meth)acrylic acid or a derivative thereof by a known method. The polyglycerol of the present invention can also be urethane-converted by reacting a portion of the hydroxyl groups with an isocyanate compound by a known method. The polyglycerol of the present invention can also be converted into an allyl ether by reacting a part of the hydroxyl groups with an allyl compound by a known method. The polyglycerol of the present invention can be alkoxysilylated by reacting some of its hydroxyl groups with an isocyanate compound, an epoxy compound, or the like having an alkoxysilyl group at its terminal by a known method.Also, it can be alkoxysilylated by a hydrosilation reaction with an allyl ether.

[0059] By using each of the derivatives thus obtained as part or all of the raw materials in resin synthesis, a resin having a polyglycerin skeleton can be obtained. Furthermore, as described above, the method for producing a polyglycerol of the present invention is advantageous in that the structure can be varied by adjusting the raw materials used and their blending ratios, and therefore a polyglycerol skeleton having the physical properties required for the intended use can be easily obtained. [Example]

[0060] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples in any way.

[0061] Example 1 Glycerin (manufactured by Sakamoto Pharmaceutical Co., Ltd.) was dehydrated for 2 hours at 120°C and 5 mmHg or less to remove water from the reaction system. 30.00 g of dehydrated glycerin and 0.15 g of sodium hydroxide were placed in a 100 mL recovery flask equipped with a Dimroth filter, a temperature sensor, a nitrogen tube, and a magnetic induction stirrer, and the temperature was raised to 140°C. Next, 46.26 g of SR-GLG (epoxy equivalent: 142, viscosity: 170 mPa·s, manufactured by Sakamoto Pharmaceutical Co., Ltd.) as (poly)glycerin (poly)glycidyl ether was added dropwise over 30 minutes. After reacting at 140°C for 7 hours, 40 mL of ion-exchanged water was added and the mixture was stirred at 90°C for 2 hours. An acidic ion-exchange resin was added and the mixture was stirred for 2 hours. The ion-exchange resin was filtered off, and the resulting filtrate was concentrated to obtain polyglycerin. The polyglycerol obtained was evaluated according to the above-mentioned measurement and calculation methods.

[0062] <Example 2> The reaction was carried out under the same conditions as in Example 1, except that 39.00 g of diglycerin (manufactured by Sakamoto Pharmaceutical Co., Ltd.) was used as the (poly)glycerin, 40.03 g of SR-GLG was used as the (poly)glycerin (poly)glycidyl ether, and 0.20 g of sodium hydroxide was used as the catalyst.

[0063] Example 3 The reaction was carried out under the same conditions as in Example 1, except that 58.50 g of polyglycerin #500 (average degree of polymerization 6, manufactured by Sakamoto Pharmaceutical Industry Co., Ltd.) was used as the (poly)glycerin, 18.07 g of SR-4GL (epoxy equivalent 170, viscosity 1700 mPa s, manufactured by Sakamoto Pharmaceutical Industry Co., Ltd.) was used as the (poly)glycerin (poly)glycidyl ether, and 0.29 g of sodium hydroxide was used as the catalyst.

[0064] Example 4 The reaction was carried out under the same conditions as in Example 1, except that 55.01 g of polyglycerin #500 was used as the (poly)glycerin, 17.00 g of SR-GLG as the (poly)glycerin (poly)glycidyl ether, 0.28 g of sodium hydroxide as the catalyst, and 4.46 g of diethylene glycol dimethyl ether as the solvent were used.

[0065] <Example 5> The reaction was carried out under the same conditions as in Example 1, except that 58.50 g of polyglycerin #500 was used as the (poly)glycerin, 18.25 g of SR-DGE (epoxy equivalent: 162, viscosity: 650 mPa s, manufactured by Sakamoto Pharmaceutical Industry Co., Ltd.) was used as the (poly)glycerin (poly)glycidyl ether, and 0.29 g of sodium hydroxide was used as the catalyst.

[0066] <Comparative Example 1> A 1 L recovery flask equipped with a temperature sensor, a nitrogen pipe, and a stirrer was charged with 700 g of glycerin and 5.25 g of sodium hydroxide. A polycondensation reaction was carried out at 260°C to obtain polyglycerin with a hydroxyl value of 960.

[0067] <Comparative Example 2> A 100 mL recovery flask equipped with a Dimroth stirrer, a temperature sensor, a nitrogen tube, and a magnetic induction stirrer was charged with 9.40 g of dehydrated glycerin and 0.075 g of 85 wt% phosphoric acid, and the temperature was raised to 120°C. 66.60 g of glycidol was added dropwise over 10 hours using a syringe pump, and the mixture was allowed to react for an additional 2 hours after the addition was complete. 30 mL of ion-exchanged water was added, and the mixture was stirred at 90°C for 2 hours, and an acidic ion-exchange resin was added and stirred for 2 hours. The ion-exchange resin was filtered off, and the resulting filtrate was concentrated to obtain polyglycerol.

[0068] <Comparative Example 3> Polyglycerol was obtained in the same manner as in Comparative Example 2, except that 2.00 g of glycerin, 0.055 g of 85 wt % phosphoric acid, and 62.75 g of glycidol were used.

[0069] <Evaluation> The contact angle was measured by the following method. For each polyglycerin, a 10% by mass aqueous solution was prepared in ion-exchanged water. A glass slide (manufactured by Matsunami Glass Co., Ltd.) was used as the substrate. Measurements were performed after leaving these at 23°C / 50% RH for one day. Using a surface tensiometer, Drop Master 500 (manufactured by Kyowa Interface Science Co., Ltd.), 1 μL of the polyglycerin aqueous solution was dropped onto the glass slide, and the contact angle was determined using θ / 2 after leaving it for one minute from the time of drop application. A contact angle of 30° or less can be evaluated as having excellent wetting properties and improved hydrophilicity of the solid surface.

[0070] Table 2 shows the evaluation results of Examples 1 to 5 and Comparative Examples 1 to 3.

[0071] [Table 2]

[0072] The results in Table 2 show that in Examples 1 to 5, polyglycerols with significantly different molecular weights could be obtained by changing the raw materials, and at the same time, polyglycerols with various degrees of branching were obtained, demonstrating that the production method of the present invention can selectively produce polyglycerols with different molecular weights and degrees of branching. [Industrial Applicability]

[0073] The method for producing polyglycerol of the present invention is preferable in that it allows for the production of polyglycerol with a controlled molecular weight and degree of branching in a simple manner.

Claims

1. A polyglycerol having a weight-average molecular weight of 300 to 25,000 and a branching degree of 0.1 to 0.

6.

2. 2. The polyglycerol according to claim 1, wherein the polydispersity is 3 or more.

3. 3. The polyglycerol according to claim 1, wherein the ratio of primary hydroxyl groups to secondary hydroxyl groups is from 30 / 70 to 50 / 50.

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