JP2002275214A - Polyvinyl alcohol-based resin and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal carboxylate group-containing polyvinyl alcohol- based resin which has excellent water solubility, excellent blocking resistance and excellent barrier property, even when receiving a heat history. SOLUTION: This metal carboxylate group-containing polyvinyl alcohol-based resin is characterized by having a thermal decomposition-initiating temperature of >=260 deg.C and a point of inflection at 150 to 200 deg.C on the differential curve of a weight loss curve on a thermal analysis by a thermogravimetry(TG).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl alcohol resin (hereinafter sometimes abbreviated as PVA) and a method for producing the same, and more particularly, to a PVA excellent in water solubility and blocking resistance and a method for producing the same. About.

[0002]

2. Description of the Related Art Conventionally, PVA has been used as a dispersant, an adhesive,
It is widely used for sizing agents, films, paper processing agents, etc., and various modifications of PVA are performed according to various uses or required performance. As a typical example, PVA modified with a carboxyl group is used as a PVA for a fiber sizing agent or a paper processing agent.
Has been put to practical use.

[0003] However, such PVA is not
It has the characteristic of being more reactive than VA, and due to its reactivity, it causes intermolecular cross-linking and the like in the production process, particularly under a heated atmosphere, and the disadvantage that the water solubility, which is a characteristic characteristic of PVA, is reduced. May be.

In order to solve such a drawback, Japanese Patent Application Laid-Open No. Sho 56-4
In Japanese Patent No. 3305, after vinyl acetate and (maleic anhydride) are copolymerized in the presence of 0.5 to 2 molar equivalents of alkali with respect to the (maleic) maleic acid, ) A method of saponifying a polyvinyl acetate-based polymer obtained by copolymerizing with maleic acid under special conditions has been proposed.

[0005]

However, even in such a method, it is difficult to completely prevent the crosslinking reaction of PVA in the above-mentioned production process. On the other hand, due to recent VOC regulations, it has been considered to remove residual solvent by performing further heat treatment more than mere drying at the time of PVA production, and to be exposed to heat treatment more than conventional drying temperature and time. In the case of PVA modified with a carboxyl group produced by the above method, there is a concern that the water solubility may be further reduced, and the carboxyl group-modified PVA whose water solubility is not impaired even when subjected to such heat treatment (heat history). It is where development of is desired.

In addition, in order to improve the water solubility of PVA, it is desirable that the PVA powder or particles can be dispersed as uniformly as possible in water and that no undissolved residue is generated. Of course, it is also an important requirement that no blocking occurs during storage and transportation.

That is, the object of the present invention is to
An object of the present invention is to provide a carboxyl group-modified (containing a metal salt of carboxylic acid) PVA which does not decrease in water solubility even when subjected to heat treatment and has excellent blocking resistance.

[0008]

The present inventors have conducted intensive studies to achieve the above object, and as a result, in thermal analysis by thermogravimetry (TG), the thermal decomposition onset temperature was 26.
0 ° C. or more, and the differential curve of the weight loss curve is 150 to 200
Containing carboxylate metal bases having no inflection point at 0 ° C
The inventors have found that VA meets the above objects, and have accomplished the present invention.

In producing such PVA, the PVA containing a metal carboxylate is treated with an alcohol containing an alkaline earth metal to replace the alkali metal with the alkaline earth metal. It has also been found that a method of washing with alcohol not containing is useful.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. PVA containing a carboxylate metal base is PVA containing a carboxyl group in its structure and can be produced by any method. For example, 1) a method of polymerizing an unsaturated monomer having a carboxyl group and a vinyl ester compound, followed by saponification with a catalyst such as an alkali metal hydroxide, and 2) an alcohol having a carboxyl group or having a carboxyl group. And a method in which a compound having a functional group such as aldehyde or thiol is used as a chain transfer agent to polymerize a vinyl ester compound, and then saponified with a catalyst such as an alkali metal hydroxide. Will be described more specifically, but is not limited thereto.

First, methods 1) and 2) above for producing a carboxyl group-containing vinyl ester polymer will be described. 1) Polymerization of a monomer having a carboxyl group and a vinyl ester compound As a monomer having a carboxyl group to be copolymerized with a vinyl ester, usually an ethylenically unsaturated dicarboxylic acid (maleic acid, fumaric acid, itaconic acid, etc.) ) Or ethylenically unsaturated dicarboxylic acid monoesters (monoalkyl maleate, monoalkyl fumarate, monoalkyl itaconate, etc.) or ethylenically unsaturated dicarboxylic acid diesters (dialkyl maleate, dialkyl fumarate, Itaconic acid dialkyl ester, etc., provided that at least one ester of the diester must be converted to a carboxyl group during saponification) or ethylenically unsaturated dicarboxylic anhydride (maleic anhydride, itaconic anhydride, etc.) Monomer and And an ester thereof. Among them, an ethylenically unsaturated dicarboxylic acid monoester is preferably used.

There are no particular restrictions on the copolymerization.
Although a known polymerization method is optionally used, solution polymerization using an alcohol such as methyl alcohol or ethyl alcohol as a solvent is usually performed. In this method, as a method for charging the monomers, first, the entire amount of the vinyl ester compound and a part of the carboxyl group-containing unsaturated monomer are charged to start polymerization, and the remaining unsaturated monomers are polymerized. Arbitrary means such as a method of adding continuously or dividedly during the period and a method of batch charging can be used. The copolymerization reaction can be performed using a known radical polymerization catalyst such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, and lauroyl peroxide, and the polymerization temperature is in the range of 50 ° C. to about the boiling point. You can choose from.

2) A vinyl ester compound is polymerized by coexisting an alcohol having a carboxyl group or a compound having a carboxyl group and having a functional group such as aldehyde or thiol as a chain transfer agent. A compound derived from a thiol having a large value is effective, and examples thereof include the following compounds.

HS— (CH ₂ ) _n —COOH (1)

[0015]

In the above formulas (1) and (2), R ₁ , R ₂ and R ₃ are each a hydrogen atom or a lower alkyl group (which may have a substituent), and n is an integer of 0 to 5 Is shown. ]

[0017] [However, in the above general formula (3), n represents an integer of 0 to 20. ]

And salts of the compounds represented by the above general formulas (1) to (3). Specific examples include mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, and 2-mercaptostearic acid.

In the present invention, considering the water solubility after heating and drying, PVA containing a carboxyl group derived from maleic acid and / or its ester derivative is preferable. It is preferable to select such an unsaturated monomer or compound having a carboxyl group.

The vinyl ester compounds used in the above 1) and 2) include vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, and versatic. Vinyl acetate, vinyl palmitate, vinyl stearate and the like are used alone or in combination, but in practice, vinyl acetate is preferably used.

Finally, the carboxyl group-containing vinyl ester polymer obtained in the above 1) or 2) is saponified. In the saponification, the obtained copolymer is dissolved in alcohol. It is carried out in the presence of a saponification catalyst. Examples of the alcohol include methanol, ethanol, and butanol, and the concentration of the copolymer in the alcohol is selected from the range of 20 to 50% by weight.

Examples of the saponification catalyst include sodium hydroxide,
It is necessary to use an alkali catalyst such as an alkali metal hydroxide or an alcoholate such as potassium hydroxide, sodium methylate, sodium ethylate or potassium methylate. It is necessary to use the catalyst in an amount of 1 to 100 mmole equivalent to the vinyl ester.

The saponification temperature is not particularly limited, but is usually 1
It is preferable to select from the range of 0 to 70 ° C, more preferably 30 to 40 ° C. The saponification reaction is usually performed for 2 to 3 hours. Although the degree of saponification (of the vinyl acetate component) of the obtained carboxyl group-containing PVA is not particularly limited, it is 50 to 95 mol% in that the effect of the present invention is remarkably obtained.
(Furthermore, 60 to 92 mol%, particularly 70 to 90 mol%)
Is preferred.

Although the content of the carboxyl group in the carboxyl group-containing PVA is not particularly limited, the content of the metal carboxylate-containing monomer component is reduced to 0 in that the effect of the present invention is remarkably obtained. 0.1 to 20 mol% (more preferably 0.5 to 15 mol%, especially 2 to 10 mol%).

Thus, a carboxyl group (carboxylate metal base) -containing PVA is obtained. The PVA containing a carboxylate metal base of the present invention can be obtained by a thermogravimetric method (TG).
The thermal decomposition temperature is 260 ° C. or higher (further 260-330 ° C., especially 260-300 ° C.,
(In particular, 260 to 280 ° C.), and the differential curve of the weight loss curve is characterized by having no inflection point at 150 to 200 ° C., and must show a thermal decomposition curve as shown in FIG. .

The thermal analysis by the thermogravimetric method (TG) referred to here means that the PVA is heated from 30 ° C. to 600 ° C. in air.
Up to 10 ° C./min to obtain a thermal weight loss curve and its derivative curve (weight loss rate curve). The decomposition start temperature can be read from the peak temperature of the former curve. 150-200 ° C from the latter curve
It is possible to check whether there is an inflection point in
For example, it can be measured by "TGA-7" manufactured by Perkin Elmer.

In order to obtain a PVA containing a metal salt of a carboxylate having such characteristics, there is no particular limitation. In the production of the carboxyl group-containing PVA, the carboxyl group-containing PVA after the saponification reaction is treated with an alkaline earth. After treating with an alcohol containing a metal, a method of treating with an alcohol containing no alkaline earth metal,
A method in which the carboxyl group-containing PVA obtained by a conventional method is treated with an alcohol containing an alkaline earth metal, and then treated with an alcohol containing no alkaline earth metal. After performing saponification in the coexistence of an alkaline earth metal, there may be mentioned a method of treating with an alcohol not containing an alkaline earth metal, and the like. Although described in more detail, the present invention is not limited to this.

The above method is based on the above-mentioned carboxyl group-containing P
In the production of VA, the carboxyl group-containing PVA after the saponification reaction is first treated with an alcohol containing an alkaline earth metal to replace the alkali metal salt in the PVA with an alkaline earth metal. Examples of the earth metal include calcium, zinc, magnesium, and barium. Preferably, calcium, zinc, and magnesium are used. Further, when considering the transparency of the obtained PVA aqueous solution, calcium is preferably used. Is preferred.

The above-mentioned alcohol containing an alkaline earth metal may be any alcohol, as long as the metal is present in the alcohol, and may be in any of a solution state, a slurry state, a dispersion state, and a simple mixed state.

In preparing the alcohol containing the alkaline earth metal, the compound containing the earth metal may be dissolved, dispersed, or mixed in the alcohol. Acetate, nitrate, sulfate, hydrochloride (chloride) and the like, among which acetate and nitrate are preferably used.

As the alcohol, methyl alcohol, ethyl alcohol, iso-propyl alcohol, n-
Propyl alcohol and the like can be mentioned, and methyl alcohol is preferably used.

The content of the alkaline earth metal in the alcohol is 1 to 5 moles (more preferably 1 to 5 times) the carboxyl group in the carboxyl group-containing PVA to be treated.
The content may be adjusted so as to be 4 mol, particularly 2 to 3 mol. When the content is less than 1 mol, the effect of improving water solubility after heating is poor, and when it exceeds 5 mol, on the contrary. It takes time and effort to remove the excess alkaline earth metal, and the alcohol may remain in the PVA obtained because a large amount of alcohol for washing is used, which is not preferable.

In treating the carboxyl group-containing PVA with an alcohol containing an alkaline earth metal as described above, the PVA may be immersed in the alcohol.
More preferably, stirring or the like is performed.

The temperature of the alcohol is preferably from 10 to 60 ° C. (more preferably from 20 to 40 ° C.). If the temperature is lower than 10 ° C., the solubility of the alkaline earth metal is reduced and the substitution efficiency is reduced. If the temperature exceeds 60 ° C., if the temperature is close to the boiling point of the alcohol, an improvement in the substitution efficiency cannot be expected, which is not preferable. The treatment time with the alcohol is preferably 20 to 120 minutes (more preferably 30 to 60 minutes). If the time is less than 20 minutes, the replacement of the alkaline earth metal may not proceed sufficiently. Exceeding minutes is not preferable because it takes too much time and becomes uneconomical.

By the treatment as described above, the alkali metal salt in the carboxyl group-containing PVA is replaced with an alkaline earth metal. PVA in which such a metal salt is substituted,
Then, it is washed with an alcohol containing no alkaline earth metal. The same alcohol as described above can be used as the alcohol when washing with an alcohol containing no alkaline earth metal.

This washing is to remove the alkaline earth metal salt and the like contained in the PVA treated (substituted with metal salt) (present in PVA without being substituted with metal or mixed with PVA). There is no restriction on the temperature of the alcohol solution or the treatment time as long as the object can be achieved, but the treatment is usually performed at a temperature of 20 to 40 ° C. for about 5 to 30 minutes.

Thereafter, through a treatment such as drying, the PVA containing the metal carboxylate of the present invention is obtained. Such PVA is excellent in water solubility even when subjected to heat history.
Excellent blocking resistance, useful for paper processing agents, fiber sizing agents, adhesives, emulsifiers, suspending agents, etc.,
The PVA according to the present invention is excellent in film-forming properties, barrier properties, chemical resistance, etc., and is therefore very useful for coating applications such as paper and films / sheets. In particular, release paper, heat-sensitive recording paper, and inkjet paper It is useful for coating applications such as

About the above-mentioned coating use of release paper
To explain, release paper is usually glassine paper or semi-glass paper.
Paper on paper, kraft paper, Japanese paper, woodfree paper, etc.
Release agents such as cone resin and fluorine resin are laminated.
Between the substrate surface and the release agent layer.
It coats the PVA with sil groups. Coat
When the PVA is used, the PVA is added in an amount of
Make aqueous solution, size press coat method, roll coater
Method, air doctor method, blade coater method, gatero
By a known coating method such as
What is necessary is just to coat, and as a coating amount of the PVA,
0.1 to 10 g / m in terms of solid content ^TwoIs preferred, and furthermore
0.5-5g / m^TwoIs preferred.

By providing a layer of the carboxyl group-containing PVA of the present invention on the surface of the substrate, a barrier layer is formed on the surface of the substrate, so that excessive penetration of the release agent can be suppressed, and a small amount of the release agent can be suppressed. To exert an effect of releasing, and an effect of improving the adhesiveness between the releasing agent layer and the base material.

[0040]

Next, the present invention will be described in more detail by way of examples. In the examples, “%” and “parts” are based on weight unless otherwise specified.

Example 1 In a polymerization vessel, 1000 parts of vinyl acetate, 1 part of maleic anhydride,
Charge 200 parts of methyl alcohol and stir the system.
After raising the temperature in a nitrogen stream and refluxing at 60 ° C. for 30 minutes, azobisisobutyronitrile was added at 0.08 mol% based on vinyl acetate, and the methyl alcohol solution of maleic anhydride was modified to a degree of denaturation of 2.0 mol. % And the mixture was reacted for 6 hours by polymerization. After completion of the polymerization, methyl alcohol vapor was blown in to remove unreacted monomers to obtain a methyl alcohol solution of a copolymer of vinyl acetate and maleic acid.

Thereafter, the concentration of the solution was adjusted to 40%,
0 ° C., and further saponified by adding 30 mmol equivalent of sodium hydroxide to vinyl acetate in the copolymer to obtain a carboxyl group-containing PVA (a saponification degree of 89 mol% and a carboxyl group content of 2.0 mol%). ) Got.

Next, the obtained PVA was immersed in methyl alcohol (25 ° C.) containing 3.0 times mol of calcium (calcium acetate) with respect to the carboxyl group content, and stirred for 60 minutes. (25 ° C)
, And filtered and dried (air-dried) to obtain PVA containing the metal carboxylate of the present invention.

The obtained PVA was subjected to a thermogravimetric method (T
When the thermal analysis according to G) was performed, the thermal decomposition curve shown in FIG. 1 was obtained. The thermal decomposition onset temperature was 262.4 ° C., and the differential curve of the weight loss curve had no inflection point at 150 to 200 ° C. Was something. The obtained PVA was evaluated for water solubility and blocking resistance as follows. In addition, the evaluation of barrier properties was performed as an evaluation of paper coating use, and the evaluation of releasability was further performed as follows in the evaluation of coating use of release paper.

(Water-soluble) The obtained PVA was treated with (A) 13
The sample was dried in hot air at 0 ° C. for 1 minute, and 25.0 g of the solution was put into a beaker containing 500 ml of water, gradually heated to 50 ° C. while stirring from room temperature, and kept at the temperature for 1 hour. Is passed through two filter cloths (80 mesh), and 85 ° C.
The insoluble matter (%) was calculated from the weight (g) of the filter cloth before and after drying for 3 hours using the following formula, and the result was defined as solubility. Insoluble content (%) = [(weight of filter cloth after filtration−weight of filter cloth before filtration) /25.0] × 100 (a) 30 minutes at 130 ° C .;
The same evaluation was performed under hot air drying conditions for 0 minutes.

(Blocking resistance) Whether or not the obtained PVA was blocked was visually observed and evaluated as follows.・ ・ ・: No blocking is observed at all △: Slight blocking is observed ×: Most of the blocks are blocked

(Barrier property) After the obtained PVA was converted into a 6% aqueous solution, acidic paper (basis weight: 65 g / m ² , tension: 0.7 g)
/ M ² ) (the solid content conversion amount of PVA is 1.8 g /
m ² ), and after drying, apply the coated paper obtained to an Oken-type air permeability tester (manufactured by Asahi Seiko Co., Ltd.) in accordance with the air permeability of JIS P 8117. The transit time (seconds) was measured.

(Releaseability) Glassine paper (basis weight 65 g /
m ² , a tension of 1.1 g / m ² ) (the solid content of PVA is 2.0 g / m ² ), and after drying, a silicone release agent (“X-” manufactured by Shin-Etsu Chemical Co., Ltd.) 52-131 ”) was applied (solid content conversion amount was 1.0 g / m ² ) to produce release paper. The surface of the obtained release paper is coated with an acrylic emulsion adhesive (“Nicazole L-14 manufactured by Nippon Carbide Co., Ltd.”).
5 ”) was applied at 25 g / m ^{2 in} terms of solid content, and
After drying with hot air, a high-quality paper having a basis weight of 65 g / m ² was laminated, and the peel strength (g / 5
cm) was measured at room temperature and evaluated as follows.・ ・ ・: Less than 100 g / 5 cm △: 100 to less than 200 g / 5 cm ×: 200 g / 5 cm or more

Example 2 The same procedures as in Example 1 were carried out except that calcium nitrate was used in place of calcium acetate, and that methyl alcohol containing calcium (calcium nitrate) at a molar ratio of 2.0 times the carboxyl group content was used. Then, the target PVA was obtained, and the evaluation was performed in the same manner. The thermal decomposition onset temperature of the obtained PVA was 268.5 ° C., and the differential curve of the weight loss curve was 1
It did not have an inflection point at 50 to 200 ° C.

Example 3 In Example 1, PV containing a metal carboxylate was used.
The target PVA was obtained in the same manner except that the saponification degree of A was changed to 78 mol% and the modification degree was set to 4.0 mol%, and the evaluation was similarly performed. The thermal decomposition start temperature of the obtained PVA was 285.4 ° C., and the differential curve of the weight loss curve was 150 to 20.
It had no inflection point at 0 ° C.

Example 4 The same procedure as in Example 1 was carried out except that zinc acetate was used instead of calcium acetate, and methyl alcohol containing zinc (zinc acetate) at a molar ratio of 3.0 times the carboxyl group content was used. To obtain the desired PVA, and similarly evaluated. The thermal decomposition onset temperature of the obtained PVA was 26.
At 3.8 ° C, the derivative curve of the weight loss curve had no inflection point at 150 to 200 ° C.

Example 5 A target PVA was obtained in the same manner as in Example 2 except that methyl alcohol containing the same mole of calcium (calcium nitrate) with respect to the carboxyl group content was used. Was done. The thermal decomposition onset temperature of the obtained PVA was 262.0 ° C., and the differential curve of the weight loss curve was 1
It did not have an inflection point at 50 to 200 ° C.

Comparative Example 1 A PVA was obtained in the same manner as in Example 1, except that the immersion treatment with methyl alcohol containing calcium (calcium acetate) and the subsequent washing with methyl alcohol were not carried out. Was evaluated. The thermal decomposition onset temperature of the obtained PVA was 249.6 ° C, and the differential curve of the weight loss curve had no inflection point at 150 to 200 ° C.

COMPARATIVE EXAMPLE 2 In Example 1, instead of methyl alcohol containing calcium (calcium acetate), calcium (a 20% aqueous solution containing calcium acetate containing 3.0% by mole of carboxyl group content of PVA) was used. A PVA was obtained and evaluated in the same manner except that a hydroalcoholic solution of calcium acetate to which 4 times by weight of methyl alcohol was added was used, and the thermal decomposition onset temperature of the obtained PVA was 252. .
At 9 ° C, the derivative curve of the weight loss curve had no inflection point at 150 to 200 ° C. Table 1 shows the evaluation results of the examples and the comparative examples.

[0055] [Table 1] resistance Bed Rokkinku Bu resistance dissolve barrier property peelability (A) (b) (c) Example 1 ○ 0.019 0.011 0.593 ○ ○ 〃 2 ○ 0.002 0.004 0.071 ○ ○ 〃 3 ○ 0.018 0.016 0.045 ○ ○ ４ 4 ○ 0.011 0.014 0.435 ○ ○ 〃 5 ○ 0.046 0.075 0.651 ○ ○ Comparative Example 1 × 0.185 67.3 100 × × 〃 2 × 0.563 0.843 23.8 △ △ Note) (a) is 130 ° C for 1 minute, (a) is 130 ° C for 30 minutes, (c) 130 ° C for 60 minutes

[0056]

The polyvinyl alcohol-based resin containing the metal carboxylate of the present invention exhibits a unique behavior in thermal analysis by a thermogravimetric method (TG), and therefore has excellent water solubility even when subjected to a thermal history. It has excellent blocking resistance, and is useful for applications such as paper processing agents, fiber sizing agents, adhesives, emulsifiers, and suspending agents. The PVA of the present invention has film-forming properties, barrier properties, and chemical resistance. It is also very useful for coating applications such as paper, film and sheet, etc.
In particular, it is useful for coating applications such as release paper, thermal recording paper, and inkjet paper.

[Brief description of the drawings]

FIG. 1 is a thermogravimetric method (TG) of a polyvinyl alcohol-based resin containing a metal carboxylate of the present invention (Example 1).
Thermal analysis curve

FIG. 2 is a thermal analysis curve of the polyvinyl alcohol-based resin of Comparative Example 1 by a thermogravimetric method (TG).

FIG. 3 is a thermal analysis curve of a polyvinyl alcohol-based resin of Comparative Example 2 by a thermogravimetric method (TG).

Claims (8)

[Claims] 1. A polyvinyl alcohol-based resin containing a metal carboxylate, wherein in a thermal analysis by thermogravimetry (TG), the thermal decomposition onset temperature is 260 ° C. or higher, and the differential curve of the weight loss curve is 150 to 150 ° C. A polyvinyl alcohol resin having no inflection point at 200 ° C. 2. The polyvinyl alcohol resin according to claim 1, wherein the carboxylic acid metal base is derived from an ethylenically unsaturated dicarboxylic acid or a derivative thereof. 3. The polyvinyl alcohol resin according to claim 2, wherein the ethylenically unsaturated dicarboxylic acid or a derivative thereof is maleic anhydride or an alkyl ester thereof. 4. The polyvinyl alcohol-based resin according to claim 1, wherein the metal in the carboxylic acid metal base is an alkaline earth metal. 5. The polyvinyl alcohol resin according to claim 4, wherein the alkaline earth metal is any of calcium, zinc and magnesium. 6. The content of the metal carboxylate-containing monomer component is 0.1 to 20 mol%, and the saponification degree is 50 to 95.
The polyvinyl alcohol resin according to any one of claims 1 to 5, which is mol%. 7. The polyvinyl alcohol-based resin according to claim 1, which is used for coating a release paper. 8. In producing the polyvinyl alcohol-based resin according to any one of claims 1 to 7, the polyvinyl alcohol-based resin containing a metal carboxylate is treated with an alcohol containing an alkaline earth metal to reduce the alkali metal. A method for producing a polyvinyl alcohol-based resin, which comprises washing with an alcohol not containing an alkaline earth metal after replacing with an alkaline earth metal.