JPH0327503B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to cement admixtures, and more specifically, modified polyvinyl alcohol having a silyl group in the molecule (hereinafter polyvinyl alcohol is abbreviated as PVA).
The present invention relates to a cement admixture consisting of: Conventionally, polymer emulsion, latex or
A method of mixing water-soluble polymers such as PVA and methylcellulose into cement is widely practiced and is known to have certain effects. However, the current situation is that even with these methods, little effect can be expected in terms of preventing the formation of a laitance layer that weakens the bending strength or surface strength, which is an essential drawback of cement. In view of the above-mentioned current situation, the present inventors conducted extensive research with the aim of improving the various properties of cement. As a result, the present inventors found that modified PVA having 0.01 to 10 mol% of silyl groups in the molecule was mixed into cement (mortar or concrete). In addition to having excellent mechanical strength such as bending, compressive strength, and abrasion resistance (surface strength),
The inventors have now completed the present invention by discovering that it is possible to provide a cement composition that dramatically improves adhesive strength to adherends. The present invention will be explained in more detail below. The silyl group in the molecule used in the present invention is 0.01~
Modified PVA containing 10 mol% may be of any type as long as it contains silicon in the molecule, but the silyl group contained in the molecule may be an alkoxyl group, an acyloxyl group, a silanol group which is a hydrolyzate thereof, or a salt thereof. Those having reactive substituents such as these are particularly preferably used. As a method for producing such modified PVA, PVA
Alternatively, a method in which silyl groups are introduced into modified polyvinyl acetate containing a carboxyl group or a hydroxyl group by post-modification using a silylating agent, or a method in which a copolymer of a vinyl ester and an olefinic unsaturated monomer containing a silyl group is introduced. Examples include a method of saponifying a polyvinyl ester having a silyl group at the end obtained by polymerizing a vinyl ester in the presence of a mercaptan having a silyl group. In the method of post-modifying PVA or modified polyvinyl acetate using a silylating agent, for example,
The silylating agent is dissolved in an organic solvent that does not react with the silylating agent, such as benzene, toluene, xylene, hexane, heptane, ether, or acetone, and powdered PVA or the modified polyvinyl acetate is suspended in the solution with stirring. The vinyl acetate unit is saponified by making the silylating agent cloudy and reacting the silylating agent with PVA or the above-mentioned modified polyvinyl acetate at a temperature ranging from room temperature to the boiling point of the silylating agent, or further using an alkali catalyst etc. Thus, a silyl group-containing modified PVA can be obtained.
The silylating agents used in post-modification include:
Organohalogensilanes such as trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, vinyltrichlorosilane, diphenyldichlorosilane, and triethylfluorosilane; organosilicon esters such as trimethylacetoxysilane and dimethyldiacetoxysilane; and trimethylmethoxysilane. , organoalkoxysilanes such as dimethyldimethoxysilane, organosilanols such as trimethylsilanol and diethylsilanediol, aminoalkylsilanes such as N-aminoethylaminopropyltrimethoxysilane,
Examples include organosilicon isocyanates such as tremethyl silicone isocyanate. The introduction rate of the silylating agent, that is, the degree of modification, can be arbitrarily adjusted by adjusting the amount of the silylating agent used and the reaction time. Also obtained is silyl group-containing modified PVA
The degree of polymerization and degree of saponification are the degree of polymerization of the PVA used,
The degree of saponification can be arbitrarily adjusted by adjusting the degree of saponification or the degree of polymerization of the above-mentioned modified polyvinyl acetate and the saponification reaction. In addition, in a method of saponifying a copolymer of a vinyl ester and a silane group-containing olefinic unsaturated monomer, for example, the vinyl ester and the silyl group-containing olefinic unsaturated monomer are combined with a radical initiator in alcohol. A silyl group-containing modified PVA can be obtained by copolymerizing the copolymer using PVA and then saponifying the copolymer by adding an alkali or acid catalyst to the alcohol solution of the copolymer. Vinyl esters used in the above method include vinyl acetate, vinyl propionate, vinyl formate, etc., but vinyl acetate is preferred from an economic standpoint. The silyl group-containing olefinic unsaturated monomers used in the above method include vinylsilane represented by the following formula (), and (meth)acrylamide represented by ().
Examples include alkylsilanes. [Here, n is 0 to 4, m is 0 to 2, R ¹ is an alkyl group having 1 to 5 carbon atoms (methyl, ethyl, etc.),
R ² is an alkoxyl group or an acyloxyl group having 1 to 40 carbon atoms (the alkoxyl group or sialoxyl group may have an oxygen-containing substituent), R ³ is a hydrogen atom or a methyl group, R ⁴ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ⁵ represents an alkylene group having 1 to 5 carbon atoms or a divalent organic residue in which chain carbon atoms are mutually bonded through oxygen or nitrogen. Note that when two R ¹ 's exist in the same monomer, R ¹ may be the same or different. Also
Even when two or more R ^2s exist in the same monomer,
R ² may be the same or different. ] Specific examples of the vinylsilane represented by formula () include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris-(β-methoxyethoxy)silane, vinyltriacetoxysilane, allyltrimethoxysilane, allyltriacetoxysilane, Vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, vinylmethyldiacetoxysilane, vinyldimethylacetoxysilane, vinylisobutyldimethoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltributoxysilane hexyloxysilane, vinylmethoxydihexyloxysilane, vinyldimethoxyoctyloxysilane,
Vinylmethoxydioctyloxysilane, vinyltrioctyloxysilane, vinylmethoxydilauryloxysilane, vinyldimethoxylauryloxysilane, vinylmethoxydioleyloxysilane, vinyldimethoxyoleyloxysilane, and general formula (Here, R ¹ and m are the same as above, and x is 1 to 20). Specific examples of the (meth)acrylamide-alkylsilane represented by the formula () include 3-(meth)acrylamide-propyltrimethoxysilane, 3-(meth)acrylamide-propyltriethoxysilane, and 3-(meth)acrylamide-propyltriethoxysilane. Acrylamido-propyltri(β-methoxyethoxy)silane, 2-(meth)acrylamido-2-methylpropyltrimethoxysilane, 2-(meth)acrylamido-2-methylethyltrimethoxysilane, N-(2-(meth)
Acrylamide-ethyl)-aminopropyltrimethoxysilane, 3-(meth)acrylamide-
Propyltriacetoxysilane, 2-(meth)acrylamido-ethyltrimethoxysilane, 1-
(meth)acrylamido-methyltrimethoxysilane, 3-(meth)acrylamido-propylmethyldimethoxysilane, 3-(meth)acrylamido-propyldimethylmethoxysilane, 3-
(N-methyl-(meth)acrylamide)-propyltrimethoxysilane, 3-((meth)acrylamide-methoxy)-3-hydroxypropyltrimethoxysilane, 3-((meth)acrylamide-methoxy)-propyltrimethoxysilane , dimethyl-3-(meth)acrylamido-propyl-3-(trimethoxysilyl)-propylammonium chloride, dimethyl-2-(meth)acrylamido-2-methylpropyl-3-(trimethoxysilyl)propylammonium chloride, etc. Can be mentioned. In addition, when copolymerizing the vinyl ester and the silicon-containing olefinic unsaturated monomer to produce the modified PVA used in the present invention, other monomers other than the above two components must be used. Other copolymerizable unsaturated monomers, such as styrene, alkyl vinyl ethers, vinyl versatate,
(meth)acrylamide, ethylene, propylene,
Olefins such as α-hexene and α-octene,
Unsaturated acids such as (meth)acrylic acid, crotonic acid, (anhydrous) maleic acid, fumaric acid, and itaconic acid; their alkyl esters and alkali salts; trimethyl-2-(1-(meth)acrylamide 1,1-
Presence of a small proportion of cationic monomers such as dimethylethyl) ammonium chloride, trimethyl-3-(1-(meth)acrylamidopropyl) ammonium chloride, 1-vinyl-2-methylimidazole, and quaternized products thereof. is also possible. In addition, in a method for saponifying a polyvinyl ester having a silyl group at the end obtained by polymerizing a vinyl ester in the presence of a mercaptan having a silyl group, for example, when vinyl ester is polymerized using a radical initiator, , a mercaptan having a silyl group is added to the polymerization system all at once, in parts, or continuously, so that the mercaptan having a silyl group is present in the polymerization system, and by chain transfer to the mercaptan, a polyvinyl ester having a silyl group at the end is produced. After the polyvinyl ester is produced, an alkali or acid catalyst is added to the alcohol solution of the polyvinyl ester to saponify the polyvinyl ester, thereby producing a modified product having a silyl group.
You can get PVA. As the mercaptan having a silyl group used in this method, 3-(trimethoxysilyl)-propyl mercaptan and the like can be used. Denatured by this method
In producing PVA, it is also possible to have a small proportion of unsaturated monomers copolymerizable with the vinyl ester used in the process. In the above-mentioned three production methods for modified PVA containing a silyl group in the molecule used in the present invention, a copolymer of a vinyl ester and an olefinic unsaturated monomer containing a silyl group is saponified. The method of saponifying a polyvinyl ester having a silyl group at the terminal obtained by polymerizing a vinyl ester in the presence of a mercaptan having a silyl group is easy to manufacture industrially and has the advantages of homogeneity of the resulting modified PVA. It is preferably used in The silyl group used in the present invention is 0.01 to 10
The degree of saponification or degree of polymerization of the modified PVA contained in mol% is appropriately selected depending on the purpose and is not particularly limited. Silyl groups are effective even in relatively small amounts, and are usually used as monomer units containing silyl groups.
It is selected from the range of 0.01 to 10 mol%, preferably 0.1 to 2.5 mol%. Saponification degree is usually 70 to 100 mol%
A range of is preferred. Further, the degree of polymerization is usually selected from the range of 10 to 3000. When dissolving the above-mentioned modified PVA used in the present invention in water, usually after dispersing the modified PVA in water, if necessary, an alkali such as sodium hydroxide is added and heated while stirring. A homogeneous aqueous solution can be obtained by The cement admixture of the present invention is used by mixing it with cement and, if necessary, fine aggregate or aggregates (for example, sand, gravel, etc.). In the present invention, the amount of modified PVA added is preferably 0.01 to 30% by weight, particularly 0.05 to 10% by weight, based on the cement. If the amount is less than 0.01% by weight, the effect is essentially the same as not adding it, and if it is more than 30% by weight, the fluidity of the cement tends to deteriorate, and it is not necessary to add such a large amount. That's because there isn't. As for the addition method, it is most convenient to use a fine powder of modified PVA having a silyl group in the molecule from the viewpoint of workability, but a method of adding an aqueous solution can also be used. The modified PVA of the present invention exhibits a high effect even when used alone, but it can be used with other admixtures such as polymer emulsion or latex, PVA,
It is also possible to use modified PVA or cellulose derivatives in combination, and depending on the purpose, good results can be obtained by using them in combination. The cement admixture of the present invention has excellent mechanical strength such as bending, compressive strength, and abrasion resistance (surface strength),
It is characterized by providing a cement composition with high adhesion to adherends. Although the reason why the admixture of the present invention has the above-mentioned remarkable performance is not fully elucidated, it is
The silyl group in modified PVA, which has 0.01 to 10 mol%, is highly reactive with calcium silicate compounds or aggregates, which are components of cement, and not only strongly bonds cement crystal particles and aggregates, but also
The water-retaining properties of PVA suppress the migration of free water from the cement to the surface, and the silyl groups in modified PVA react with calcium hydroxide, which is abundant in free water, resulting in hydroxylation on the cement surface. It is presumed that the remarkable performance described above is achieved by suppressing the formation of a weak layer (laitance layer) containing calcium as a main component. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto. In the examples, unless otherwise specified, "%" and "part" represent weight standards. Example 1, Comparative Examples 1 and 2 A copolymer of vinyltrimethoxysilane and vinyl acetate was saponified to contain 0.2 mol% of silyl groups as vinylsilane units, saponification degree of vinyl acetate unit was 98.5 mol%, degree of polymerization A modified PVA with 2000 silyl groups in the molecule was obtained. 0.5 part of this modified PVA fine powder was added to 100 parts of Boltland cement and 300 parts of Toyoura standard sand, and further 65 parts of water was added and kneaded so that the mortar flow value was 170.
It was molded according to JIS-R5201 "Physical Test Methods for Cement" and its strength was measured after curing for 4 weeks under standard conditions (20°C, 65% RH). Furthermore, this was immersed in water to determine whether calcium hydroxide was leached from the cement. After 20 minutes, the mixed mortar was applied to a pre-prepared mortar board (cement-sand 1:2 cured for 4 weeks, 40 x 40 mm) to a thickness of 3 mm, and a slate board was immediately attached. Combined. After curing under standard conditions for 4 weeks, the adhesive strength was measured using a measuring jig with an autobluff at a tensile speed of 1 mm/min. The measurement results are shown in Table 1. For comparison, an example of the case where the modified PVA in Example 1 is not used (Comparative Example 1) or the case where unmodified PVA (saponification degree 90 mol%, polymerization degree 1800) is used (Comparative Example 2) The results of measurements conducted in the same manner as in 1 are also shown in Table 1. The composition of the present invention (Example 1), which uses modified PVA having a silyl group in the molecule, has significantly superior mortar strength and adhesive strength, as well as significantly less elution of calcium hydroxide, compared to each comparative example. I understand that.

[Table] The higher the value, the greater the elution.
Examples 2 to 4 The same procedure as in Example 1 was carried out except that the following modified PVA was used instead of the modified PVA used in Example 1. The results are shown in Table 2. Both strength,
It can be seen that the adhesive strength is high. Example 2: Contains 0.3 mol% of silyl groups obtained by saponifying a copolymer of vinyltriacetoxysilane and vinyl acetate as vinylsilane units,
Saponification degree of vinyl acetate unit is 99.0 mol%, polymerization degree
2000 modified PVA. Example 3: Dimethyl-2-acrylamide-2
- Contains 0.2 mol% of silyl groups obtained by saponifying a copolymer of methylpropyl-3-trimethoxysilylpropylammonium chloride and vinyl acetate as acrylamide units, saponification degree of vinyl acetate units is 93 mol%, polymerization Degeneration of degree 1750
PVA. Example 4: Contains 2 mol% of silyl group units obtained by saponifying a modified polyvinyl acetate having a silyl group at the terminal obtained by polymerizing vinyl acetate in the presence of 3-trimethoxysilylpropyl mercaptan, and acetic acid. A 10% aqueous solution of modified PVA with a vinyl unit saponification degree of 99.0 mol% and a polymerization degree of 50.

【table】

Claims (1)

[Scope of Claims] 1. A cement admixture made of modified polyvinyl alcohol having 0.01 to 10 mol% of silyl groups in the molecule. 2. The cement admixture according to claim 1, wherein the modified polyvinyl alcohol is a saponified copolymer of a vinyl ester and an olefinic unsaturated monomer having a silyl group in the molecule. 3. The cement admixture according to claim 2, wherein the olefinic unsaturated monomer is vinylalkoxysilane. 4. The cement admixture according to claim 2, wherein the olefinic unsaturated monomer is (meth)acrylamide-alkylalkoxysilane. 5. The cement admixture according to claim 1, wherein the modified polyvinyl alcohol is a saponified product of a polyvinyl ester having a silyl group at the end obtained by polymerizing a vinyl ester in the presence of a mercaptan having a silyl group.