JP4946387B2 - Method for the determination of maleic anhydride content of polymers - Google Patents

Description

  The present invention relates to a method for quantifying the content of maleic anhydride contained in a polymer containing a maleic anhydride-derived component as a structural unit.

  A polymer containing a maleic anhydride-derived component as a structural unit, such as a polymer obtained by graft polymerization of maleic anhydride, is an advantageous polymer in terms of both cost and physical properties, and is therefore used in various fields such as coating of electric wires. Yes.

  Here, since the physical properties of the polymer vary depending on the content of maleic anhydride contained in the polymer, when using a polymer containing a maleic anhydride-derived component as a constituent unit, the content of maleic anhydride is It is necessary to be appropriately controlled, and for that purpose, it is necessary to establish a method capable of accurately and relatively easily measuring the content of maleic anhydride.

  As a method for quantifying the amount of maleic anhydride contained in a polymer, for example, Non-Patent Document 1 discloses a copolymer as a method for quantifying the maleic anhydride content in a styrene / maleic anhydride copolymer (SMA). Is dissolved in toluene, and titration is performed using thymol blue as an indicator and sodium methoxide solution as a titrant. In the titration, the end point of titration is a point at which deep blue color is maintained for 1 minute or more.

  In Patent Document 1, as a method for quantifying maleic anhydride contained in a polymer obtained by graft polymerization of maleic anhydride, the graft polymer is heated and dissolved in an aromatic compound solvent, and maleic anhydride in the solution is dissolved. A method is disclosed in which acid is titrated with an alcohol solution of an alkali metal hydroxide using phenol red as an indicator.

However, all of the above methods are manual titrations using a buret, and the following problems occur, for example, when manual titration is performed. (I) In addition to the reduction of artificial deviations by the analyst (end point determination, scale reading), it is necessary for the measurer to have equipment handling education. (Ii) Since the indicator discoloration is visually determined, an indicator error is caused due to the discoloration region of the indicator as compared with the end point determination by electronic control such as pH and potential. (Iii) In manual titration, it is easy to add an excessive titrant to the equivalence point, and a titration error occurs, resulting in a decrease in analysis accuracy.
Japanese Patent Laid-Open No. 2002-202301 Japan Society for Analytical Chemistry, Polymer Analysis Research Roundtable, “Polymer Analysis Handbook”, January 12, 1995, first edition, published by Kinokuniya, p650-651

  The present invention has been made to solve the above-mentioned problems, and its purpose is to accurately and easily determine the content of maleic anhydride contained in a polymer containing a maleic anhydride-derived component as a constituent unit. It is to provide a method that can.

  The present invention is a method for quantifying the content of maleic anhydride contained in a polymer containing a maleic anhydride-derived component as a structural unit, wherein (a) in the polymer containing the maleic anhydride-derived component as a structural unit Contains a maleic anhydride-derived component from which free maleic anhydride has been removed using a free acid removal step that removes free maleic anhydride by extraction, and (b) an aromatic solvent and an alcohol solvent. A polymer solution preparation step of dissolving a polymer to be obtained to obtain a polymer solution; and (c) a potentiometric titration step in which potentiometric titration is performed on the polymer solution using an alkali metal alkoxide solution. Provide a method.

  Here, the polymer containing the maleic anhydride-derived component as a constituent unit may be a polymer obtained by grafting maleic anhydride.

  The extraction in the step (a) is preferably performed using a high speed solvent extraction method.

  The aromatic solvent is preferably toluene, and the alcohol solvent is preferably ethanol. The ratio of the aromatic solvent to the alcohol solvent and the amount of the aromatic solvent / the amount of the alcohol solvent in the polymer solution is preferably 50/5 to 50/50 by volume ratio.

  According to the present invention, the content of maleic anhydride contained in a polymer containing a maleic anhydride-derived component as a structural unit can be quantified accurately and simply.

The method of quantifying the content of maleic anhydride contained in the polymer containing the maleic anhydride-derived component of the present invention as a structural unit is the following steps (a) to (c):
(A) a free acid removal step of removing free maleic anhydride in a polymer containing a maleic anhydride-derived component as a structural unit by extraction;
(B) A polymer solution preparation step in which an aromatic solvent and an alcohol solvent are used to dissolve a polymer containing the maleic anhydride-derived component from which the free maleic anhydride has been removed as a constituent unit to obtain a polymer solution. ,
(C) The polymer solution includes a potentiometric titration step of performing potentiometric titration using an alkali metal alkoxide solution. Hereinafter, each step will be described in detail.

<Free acid removal step>
In this step, free maleic anhydride contained in the polymer containing the maleic anhydride-derived component to be measured as a constituent unit is removed by extraction (step (a)). Here, the polymer to be measured by the quantification method of the present invention is a polymer containing a maleic anhydride-derived component as a structural unit. Examples of such a polymer include maleic anhydride, maleic anhydride and Examples thereof include a copolymer with a copolymerizable monomer, a polymer, or a maleic anhydride-modified product of the copolymer. More specifically, although not particularly limited, maleic anhydride graft polymer of polyolefin such as polyethylene, polypropylene, ethylene vinyl acetate copolymer (EVA), maleic anhydride graft polymer of styrene elastomer, hydrogenated styrene system Mention may be made, for example, of an elastomeric maleic anhydride graft polymer.

  In this specification, free maleic anhydride is maleic anhydride contained in a polymer sample containing a maleic anhydride-derived component to be measured as a constituent unit, and is an unreacted component in the production of the polymer. Means maleic anhydride remaining in the polymer sample.

  In this step, such free maleic anhydride is removed by an extraction operation, which makes it possible to more accurately measure the content of maleic anhydride constituting the polymer to be measured.

  The extraction method used in this step is not particularly limited, and a conventionally known method can be employed. Specific examples include a high-speed solvent extraction method and a Soxhlet extraction method. In the high-speed solvent extraction method, extraction is performed while keeping a sample and a solvent at a high temperature and high pressure in a sealed pressure-resistant vessel. In the high-speed solvent extraction method, when the extraction time is very short compared with the Soxhlet extraction method, and the polymer sample to be measured has a pellet form of about 5 mm diameter, the extraction operation should be pulverized. This is an advantageous extraction method because it is not necessary. On the other hand, the Soxhlet extraction method requires a relatively long extraction time of about 18 hours. In order to effectively remove free maleic anhydride, the polymer sample is pulverized to a particle size of about 100 μm by freeze pulverization or the like. It is necessary to keep. In addition, when using a high-speed solvent extraction method, when a polymer sample is too large, it is preferable to cut | disconnect to an appropriate size.

  The extraction conditions in the high-speed solvent extraction method depend on the type of polymer to be measured, and thus cannot be generally specified. For example, the extraction temperature can be about 50 to 180 ° C. As the extraction solvent, acetone, hexane, Chloroform, methanol, water and the like can be used.

  After the extraction operation, the polymer sample is dried to remove the extraction solvent. Drying may be reduced pressure drying or drying under normal pressure. The drying temperature is appropriately selected according to the type of extraction solvent used.

<Polymer solution preparation process>
In this step, the polymer sample from which the free maleic anhydride has been removed is dissolved using an aromatic solvent and an alcohol solvent to obtain a polymer solution (step (b)). As described above, by using a mixed system of an aromatic solvent and an alcohol solvent as a solvent for preparing the polymer solution, the detection potential at the time of potentiometric titration can be stabilized. A maleic anhydride content can be obtained. That is, in the present invention, as described later, an alcohol solution of an alkali metal alkoxide is typically used as the titrant, and the internal solution of the electrode used for potentiometric titration is also an alcohol solution. When prepared using only an aromatic solvent, since the diffusion of the titrant and the electrode internal solution in the aromatic solvent is very slow, potential anomaly detection occurs during potentiometric titration. By using a mixed system of an aromatic solvent and an alcohol solvent, diffusion of the titrant and the electrode internal solution is promoted, so that stable measurement values can be obtained in potentiometric titration.

  Although it does not specifically limit as an aromatic solvent, Benzene, toluene, ethylbenzene, o-xylene, m-xylene, p-xylene, etc. can be mentioned. The aromatic solvent is preferably one that dissolves the polymer sample to be measured relatively well. As an aromatic solvent, only one type of solvent may be used, or two or more types may be mixed and used. Although it does not specifically limit as an alcohol solvent, Methanol, ethanol, 1-propanol, 2-propanol, a butanol, ethylene glycol etc. can be mentioned. Of these, ethanol is preferable because it is more safe than methanol. As the alcohol solvent, only one type of solvent may be used, or two or more types may be mixed and used.

  The mixing ratio of the aromatic solvent and the alcohol solvent is not particularly limited and varies depending on the type of the specific solvent and the type of polymer to be measured, but the capacity of the aromatic solvent / alcohol solvent The ratio is preferably about 50/5 to 50/50. When the amount of alcohol solvent is less than this, the detection potential at the time of potentiometric titration becomes unstable, and accurate potentiometric titration may be difficult. Moreover, when there are more alcoholic solvents than this, there exists a possibility that a polymer sample may not melt | dissolve. The volume ratio of the aromatic solvent / alcohol solvent is more preferably about 50/5 to 50/30, further preferably 50/5 to 50/20, and particularly preferably about 50/10. Further, the amount of the mixed solvent with respect to the polymer sample is not particularly limited, and may be an amount capable of dissolving the polymer sample.

  The method for preparing the polymer solution using the aromatic solvent and the alcohol solvent is not particularly limited. For example, after a polymer sample is dissolved in an aromatic solvent, an alcohol solvent is added to the polymer sample, or a mixed solvent of an aromatic solvent and an alcohol solvent is prepared in advance, and then the polymer sample is added thereto. And a method of dissolving them. In order to dissolve the polymer sample, heat treatment may be performed as necessary.

<Potentiometric titration process>
Next, potentiometric titration is performed on the polymer solution using an alkali metal alkoxide solution (step (c)). For the potentiometric titration, an automatic potentiometric titration apparatus is used. As the automatic potentiometric titration apparatus, a commercially available general apparatus can be used. Examples of the alkali metal alkoxide solution used as the titrant include, but are not limited to, a methanol solution of sodium methoxide, an ethanol solution of sodium ethoxide, and the like.

  Here, in the potentiometric titration using the potentiometric automatic titration apparatus, it is preferable that the liquid junction part of the reference electrode used is a sleeve type. By using the sleeve-type reference electrode, it is possible to prevent the liquid junction from being coated with the polymer sample, and to prevent potential abnormality detection.

  In potentiometric titration using an automatic potentiometric titrator, the end point of titration is the inflection point of the obtained titration curve. The titration amount of the titrant at the inflection point is read and applied to the following equation (1) to calculate the maleic anhydride content in the polymer sample.

Maleic anhydride content (mass%) = 100 × {(molar concentration of titrant) × V / 1000 × 98 × f} / 2W (1)
Here, in the above formula (1), the unit of the molar concentration of the titrant is mol / L, V is the titration amount (mL) of the titrant, and “98” is the molecular weight of maleic anhydride (g / L mol), W is the mass (g) of the dried polymer sample from which free maleic anhydride has been removed, “2” is the valence of maleic anhydride, and f is the calibration factor of the titrant. .

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
0.1 g of pelletized hydrogenated styrene-based thermoplastic elastomer modified with maleic anhydride (Taftec (registered trademark) M1913, manufactured by Asahi Kasei Co., Ltd.) is used in a high-speed solvent extraction method (use apparatus: ASE300 manufactured by Dionex), solvent: acetone, Extraction temperature: 100 ° C.), solvent extraction was performed to remove free maleic anhydride content in the sample. The time required was about 0.5 hours. The sample was then vacuum dried at 90 ° C. for 1 hour. Next, 50 mL of toluene was added to 0.05 g of the dried polymer sample and dissolved at room temperature, and then 10 mL of ethanol was further added and mixed to prepare a polymer solution. Next, potentiometric titration was performed using an automatic potentiometric titrator (AT610, manufactured by Kyoto Electronics Industry Co., Ltd.). A 0.05 mol / L sodium methoxide / methanol solution (calibration coefficient f = 1.012) was used as the titrant. The indicator electrode was a glass electrode, and the reference electrode was a sleeve-type liquid junction (internal liquid: 1M LiCl / ethanol solution). The titration curve obtained by potentiometric titration is shown in FIG. Circles in FIG. 1 indicate inflection points. The titration volume of the titrant at the inflection point of the titration curve was 1.78 mL. The following formula (1):
Maleic anhydride content (mass%) = 100 × {(molar concentration of titrant) × V / 1000 × 98 × f} / 2W (1)
By substituting each numerical value, the maleic anhydride content = 1.85% was obtained. In addition, the value measured by the conventional method (for example, Asahi Kasei method) is 1.79%, and a substantially equivalent value is obtained.

<Example 2>
Instead of a maleic anhydride modified product of hydrogenated styrene-based thermoplastic elastomer (Tuftec (registered trademark) M1913 manufactured by Asahi Kasei Co., Ltd.), 100 parts by mass of polyethylene, 6 parts by mass of maleic anhydride, dicumyl peroxide (DCP) 2 parts by weight, hindered phenolic antioxidant 0.5 part by weight was added and water was removed in the same manner as in Example 1 except that a sample prepared by kneading at 180 ° C. using a biaxial mixer was used. The maleic acid content was quantified. A titration curve obtained by potentiometric titration is shown in FIG. The titration amount of the titrant at the inflection point of the titration curve was 3.01 mL. From this, the maleic anhydride content was calculated to be 2.55%. In addition, the value measured by the conventional method (for example, Asahi Kasei method) is 2.62%, and a substantially equivalent value is obtained.

<Comparative Example 1>
A polymer solution was prepared in the same manner as in Example 1 except that only toluene was used for preparing the polymer solution. Next, when potentiometric titration was performed using the same automatic potentiometric titrator as in Example 1, the potential was detected abnormally, and a normal titration curve could not be obtained. The obtained titration curve is shown in FIG.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

2 is a graph showing a titration curve obtained by potentiometric titration in Example 1. FIG. 3 is a graph showing a titration curve obtained by potentiometric titration in Example 2. 3 is a graph showing a titration curve obtained by potentiometric titration in Comparative Example 1.

Claims (5)

A method for quantifying the content of maleic anhydride contained in a polymer containing a maleic anhydride-derived component as a structural unit,
(A) free maleic anhydride in a polymer containing a maleic anhydride-derived component as a constituent unit is removed by extraction;
(B) A polymer solution preparation step in which an aromatic solvent and an alcohol solvent are used to dissolve a polymer containing the maleic anhydride-derived component from which the free maleic anhydride has been removed as a constituent unit to obtain a polymer solution. When,
(C) A potentiometric titration step of performing potentiometric titration on the polymer solution using an alkali metal alkoxide solution.   The method according to claim 1, wherein the polymer containing the maleic anhydride-derived component as a constituent unit is a polymer obtained by graft polymerization of maleic anhydride.   The method according to claim 1 or 2, wherein the extraction in the step (a) is performed using a high-speed solvent extraction method.   The method according to claim 1, wherein the aromatic solvent is toluene and the alcohol solvent is ethanol.   The ratio of the aromatic solvent to the alcohol solvent and the amount of the aromatic solvent / the amount of the alcohol solvent in the polymer solution is 50/5 to 50/50 in volume ratio. The quantification method in any one of.

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