JP3436920B2 - Admixture for hydraulic compositions - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an admixture for a hydraulic composition such as cement.

[0002]

Various admixtures are used for the purpose of improving the fluidity, viscosity, flow retention and retardation of hydraulic compositions such as concrete, but these physical properties are still well balanced. No admixture to fill has been found.

Up to now, the development of dispersants of naphthalene type, melamine type, and polycarboxylic acid type has been promoted (Japanese Patent Laid-Open No. Sho 6-62).
2-70250, JP-A-62-70252, JP-A-62-78137), and JP-A-8-12396 for the purpose of improving the retention of the polycarboxylic acid-based dispersant.
JP-A-7-247150 and JP-A-10-8154.
No. 9 is disclosed.

[0004]

However, when the retention of the dispersant is improved by the method reported hitherto, the paste viscosity in the hydraulic composition becomes high, and the workability needs to be improved. Further, a compound disclosed in JP-A-8-505082, which comprises at least one phosphonic acid aminoalkylene group and at least one polyoxyalkylene group, has a low viscosity and a high retention property to a hydraulic composition. However, it shows an extremely large delay in setting, and extension of construction time becomes a problem. In addition, WO9947468A1 discloses that these compounds are compounded with a polycarboxylic acid-based dispersant having a low degree of polymerization polyoxyethylene group, but the balance between fluid retention, low viscosity, and setting retardation is unsatisfactory. There is a demand for an admixture for hydraulic compositions, which is sufficient and in which these are appropriately balanced.

[0005]

The present invention provides (A) a compound having at least one phosphonic acid group (a1) and at least one polyoxyalkylene group (a2) or a salt thereof [hereinafter referred to as (A) Component], and (B) a polymer or copolymer obtained by polymerizing a monomer mixture containing an ethylenically unsaturated monomer having a polyoxyalkylene group having an average polymerization degree of 20 to 300 [hereinafter, ( B) component]
And an admixture for a hydraulic composition containing

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION <Component (A)> The component (A) has at least one phosphonic acid group (a1). The phosphonic acid group (a1) is represented by the following general formula, and may form a phosphoric acid ester bond in the compound.

[0007]

[Chemical 1]

[M may be the same or different and each may be substituted with a hydrogen atom, an alkali metal, an alkaline earth metal, an ammonium group or a hydroxyl group,
It is a di-, tri-alkyl (C2-5) ammonium group. ].

The component (A) has at least one polyoxyalkylene group (a2). In the polyoxyalkylene group (a2), the average degree of polymerization of the oxyalkylene group, that is, the average number of moles added is 1 to 300, preferably 5 to 200. The oxyalkylene group is preferably one having 1 to 4 carbon atoms, more preferably an oxyethylene group, an oxypropylene group or a mixture thereof, most preferably an oxyethylene group. In the case of mixing oxyethylene groups and oxypropylene groups, the ratio of the average degree of polymerization of oxyethylene groups (hereinafter referred to as EOp) and the average degree of polymerization of oxypropylene groups (hereinafter referred to as POp) is EOp / [ EOp + POp] = 0.3-1 and more preferably 0.75-1.

Further, the component (A) preferably has 1 to 5, more preferably 1 to 2, and especially 1 polyoxyalkylene group (a2) in the molecule, and the group (a) in the component (A) is preferable.
The ratio of the number of 1) to the number of groups (a2) is (a1) / (a2)
≧ 1 is preferable, 5 ≧ (a1) / (a2) ≧ 1 is more preferable, (a1) / (a2) = 1 or 2 is particularly preferable, and (a1) / (a2) = 2 is most preferable.

As the component (A), the following general formula (a-
The compounds represented by i) to (a-iii) are preferred, and the compounds (ai) and (a-ii) are more preferred.

[0012]

[Chemical 2]

[Wherein X: -R,

[0014]

[Chemical 3]

RO- (AO) _n -R ^a1- , at least one of which is

[0016]

[Chemical 4]

R is a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, preferably an alkyl group, particularly preferably a methyl group, and most preferably R is a hydrogen atom or a methyl group AO: an oxy group having 2 to 3 carbon atoms. Alkylene group n: average degree of polymerization, 1 to 300, preferably 5 to 2
The number R ^a1 and R ^{a2 of} 00 may be the same or different, and each is an alkylene group having 1 to 5 carbon atoms m: 1 to 6 p: 0 to 5, preferably an integer M of 0: may be the same or different. Well, each hydrogen atom,
Alkali metals, alkaline earth metals, optionally an ammonium group or a hydroxyl substituted mono-, di-, trialkyl (2 to 5 carbon atoms) ammonium group, preferably a hydrogen atom, Na, K, NH _4, mono-, di- , Triethanol ammonium. ].

In the general formula (a-i), X is

[0019]

[Chemical 5]

It is preferable that m = 1 to 3, especially m.
= 1 is preferable, R ^a1 is an alkylene group having 2 carbon atoms, R ^a2
Is preferably an alkylene group having 1 carbon atom.

<Component (B)> As the component (B), an ethylenically unsaturated carboxylic acid ester having a polyoxyalkylene group having an average degree of polymerization of 20 to 300 and an average degree of polymerization of 2 are used.
Includes one or more monomers (b1) selected from alkenyl (C3-5) ether having a polyoxyalkylene group of 0 to 300, and an ethylenically unsaturated mono- or dicarboxylic acid or salt thereof (b2). A copolymer (B1) obtained by polymerizing a monomer mixture is preferable. Monomer (b
As 1), an ethylenically unsaturated carboxylic acid ester having a polyoxyalkylene group having an average degree of polymerization of 20 to 300 is preferable. Monomers (b1) and (b2) are each 2
You may use together 1 or more types.

The copolymer (B1) has the following general formula (b)
-I) at least one of the monomers represented by (bi) and at least one of the monomers represented by the following general formula (b-ii):
Those obtained by copolymerizing with the seed (bii) are preferable.
The monomers (bi) and (bii) may be used in combination of two or more kinds.

[0023]

[Chemical 6]

[Wherein R ¹ and R ^{2 are a} hydrogen atom or a methyl group m: the number of 0 to 2 R ³ : a hydrogen atom or —COO (AO) _n X p: the number of 0 or 1 AO: the number of carbon atoms 2] 4 to oxyalkylene group or oxystyrene group n: average degree of polymerization 20 to 300, preferably 50 to
Number Y of 150: represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. ]

[0025]

[Chemical 7]

[In the formula, R ^{4 to} R ^{6 are a} hydrogen atom, a methyl group or (CH ₂ ) _{m 1} COOM ²
And (CH ₂ ) _m1 COOM ² is COOM ¹ or another (CH 2
₂ ) An anhydride may be formed with _m1 COOM ² , in which case M ¹ and M ² of those groups are not present. M ¹ , M ² : a hydrogen atom, an alkali metal, an alkaline earth metal, an ammonium group or a mono-, di-, or trialkyl (having 2 to 5 carbon atoms) ammonium group which may be substituted with a hydroxyl group m 1 to 0 to 2 Represents ].

The monomer (b) represented by the general formula (b-i)
As i), a (half) ester of (meth) acrylic acid or maleic acid with a polyalkylene glycol capped with one terminal alkyl such as methoxypolyethylene glycol, methoxypolypropylene glycol, methoxypolybutylene glycol, methoxypolystyrene glycol, or ethoxypolyethylene polypropylene glycol Compound, 3-
Methyl-3-butenyl alcohol, etherified product with (meth) allyl alcohol, and addition of ethylene oxide and propylene oxide to (meth) acrylic acid, maleic acid, 3-methyl-3-butenyl alcohol, (meth) allyl alcohol Things can be mentioned. R ³ is preferably a hydrogen atom, p is preferably 1, and m is preferably 0. AO is preferably an oxyethylene group. As the monomer (bi),
Alkoxy, particularly esterified products of methoxy polyethylene glycol and (meth) acrylic acid are more preferable.

The monomer (bii) represented by the general formula (b-ii) includes monocarboxylic acid type monomers such as (meth) acrylic acid and crotonic acid, maleic acid, itaconic acid,
A dicarboxylic acid monomer such as fumaric acid, or an anhydride or salt thereof, such as an alkali metal salt, an alkaline earth metal salt, an ammonium salt, or a mono-, di-, or trialkyl (having a carbon number) in which a hydroxyl group may be substituted. 2-8) Ammonium salt is preferable, more preferably (meth) acrylic acid, maleic acid, maleic anhydride, and further preferably (meth) acrylic acid or an alkali metal salt thereof.

The molar ratio of the monomer (bi) to the monomer (bii) is (bii) / (bi) = 40/60 to 99/1, more preferably 60/40 to 95/5.

The polymerization reaction of the monomer mixture containing the ethylenically unsaturated monomer, preferably the monomer mixture containing the monomer (bi) and the monomer (bii), is carried out without a solvent or in the presence of a solvent. You may go below. Examples of the solvent include water, lower alcohols such as methanol, ethanol, isopropanol and butanol; aromatic hydrocarbons such as benzene, toluene and xylene; alicyclic hydrocarbons such as cyclohexane; aliphatic hydrocarbons such as n-hexane; acetic acid. Examples thereof include esters such as ethyl; ketones such as acetone and methyl ethyl ketone. Among these, water and lower alcohols are preferable from the viewpoints of easy handling and solubility of the monomer and polymer.

In the polymerization reaction, a polymerization initiator can be added. As the polymerization initiator, an organic peroxide,
Examples thereof include inorganic peroxides, nitrile compounds, azo compounds, diazo compounds, sulfinic acid compounds and the like. The addition amount of the polymerization initiator is preferably 0.05 to 50 mol% with respect to the total of all monomers.

A chain transfer agent may be added in the polymerization reaction. As the chain transfer agent, lower alkyl mercaptan, lower mercapto fatty acid, thioglycerin,
Examples thereof include thiomalic acid and 2-mercaptoethanol. The reaction temperature of the polymerization reaction is preferably 0 to 120 ° C.

The obtained polymer or copolymer can be deodorized if necessary. In particular, when a thiol such as mercaptoethanol is used as a chain transfer agent, an unpleasant odor tends to remain in the polymer, and therefore deodorizing treatment is desirable.

When the polymer or copolymer of the component (B) is a polycarboxylic acid type polymer, it can be used as a dispersant for cement even in the acid form, but it suppresses hydrolysis of the ester due to acidity. From the viewpoint, it is preferable that the salt form is obtained by neutralization with an alkali. Examples of the alkali include hydroxides of alkali metals or alkaline earth metals, ammonia, mono-, di-, and trialkyls (C2-C2).
8) amine, mono, di, trialkanol (C2-C2
8) An amine etc. can be mentioned. When a (meth) acrylic acid-based polymer is used as a dispersant for cement,
Partial or complete neutralization is preferred.

Weight average molecular weight of component (B) [gel permeation chromatography method, polyethylene glycol conversion, column: G4000PWXL + G2500P
WXL (manufactured by Tosoh Corporation), eluent: 0.2 M phosphate buffer / acetonitrile = 7/3 (volume ratio)] is preferably 1,000 to 200,000, and preferably 10,000 to obtain sufficient dispersibility. ~ 1
0,000 is more preferable, and 25,000 to 80,000 is particularly preferable.

In producing the component (B), acrylonitrile, (meth) acrylamide, styrene, alkyl (meth) acrylate (having 1 to 12 carbon atoms which may have a hydroxyl group) ester, Methallyl sulfonic acid, styrene sulfonic acid, phosphoethyl methacrylate, sulfoethyl methacrylate, average degree of polymerization 20
A copolymerizable monomer such as an ethylenically unsaturated monomer having a polyoxyalkylene group of less than or more than 300 may be used in combination. These are 50% by weight or less in all monomers, and further 3
It can be used in a proportion of 0% by weight or less, but 0% by weight is preferable.

<Admixture for hydraulic composition> In the present invention, the weight ratio of the components (A) and (B) is (A) /
(B) = 95/5 to 1/99 is preferable, 70/30 to
10/90 is more preferable, and 50/50 to 20/80 is more preferable.

It is preferable to use an antifoaming agent in combination with the admixture of the present invention from the viewpoint of antifoaming property.
(1) Lower alcohols such as methanol and ethanol,
(2) Silicone type such as dimethyl silicone oil and fluorosilicone oil, (3) Mineral oil type such as a mixture of mineral oil and surfactant, (4) Phosphate ester type such as tributyl phosphate, (5) Olein Examples thereof include acids, sorbitan oleic acid monoesters, fatty acid esters such as polyethylene glycol fatty acid esters and polyethylene / polypropylene glycol fatty acid esters, and ester systems thereof, and nonionic systems such as (6) polypropylene glycol and polyethylene / polypropylene glycol alkyl ethers.
(4) Phosphate ester type, (5) fatty acid or its ester type, more preferably polyethylene /
Polypropylene glycol fatty acid ester. The addition amount of the defoaming agent is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, and 0.1 to 3 parts by weight with respect to 100 parts by weight (solid content) of the component (B). Particularly preferred.

The admixture of the present invention is a high-performance water reducing agent,
You may contain various additives (materials), such as an AE agent, a retarder, a foaming agent, a waterproofing agent, and a preservative. Those known in the art are used. Furthermore, blast furnace slag, fly ash,
Fine powder such as silica fume and stone powder may be blended.

A hydraulic composition can be obtained from the admixture for hydraulic composition of the present invention, cement, fine aggregate, and coarse aggregate. The admixture of the present invention is 0.01 to 3.0% by weight (as solid content), particularly 0.05 to 1.0% by weight, based on the hydraulic powder (preferably cement) in the hydraulic composition. It is preferable to mix them in a ratio of. Applications of hydraulic compositions also include aerated (light) concrete, heavy concrete, waterproof concrete, mortar, hot mix concrete, underwater non-separable concrete, prepacked concrete, tremie concrete, grout, concrete for filling steel pipes, cold concrete, hot concrete. , Self-leveling material, plaster, coal / water slurry, gypsum / water slurry, by-product gypsum / water slurry, etc., but are not limited.

[0041]

Example 1 Production Example 1 A base such as diphenylmethyl potassium was added to an anhydrous tetrahydrofuran solution of ethanolamine in an inert atmosphere in accordance with the example of Japanese Patent Publication No. 8-505082, and then alkylene oxide (hereinafter , AO) Addition (AO
The type A and the average degree of polymerization are shown in Table 1).
Formaldehyde was added and reacted in the presence of hydrochloric acid to a mixture of the O adduct and a phosphoric acid in a 2-fold molar amount to obtain various target compounds shown in Table 1.

[0042]

[Table 1]

(Note) In the table, EO is oxyethylene group, P
O is an oxypropylene group, and the number next to each is the average degree of polymerization of each (the same applies hereinafter).

Production Example 2 Methoxy polyoxyalkylene glycol (type of AO, average degree of polymerization is as shown in Table 3) was placed in a glass reaction vessel.
00 g, platinum catalyst / C carrier 100 g and water 9000 g were charged, and the mixture was heated and stirred at 70 ° C. for 24 hours while blowing oxygen. After filtering the catalyst, the water content is reduced to 1% by vacuum filtration.
In the following, methoxypolyoxyalkylenecarboxylic acid was obtained. 2.7 mol of this methoxy polyoxyalkylene carboxylic acid, 2.3 mol of phosphorous acid (H ₃ PO ₃ ) and 290 g of sulfolane (solvent) were put into a reaction vessel, and the amount of 85 to 85
Melted at 90 ° C. To this, phosphorus chloride (PCl ₃ ) 25
After 0 g was added dropwise and reacted at 90 ° C. for 25 hours, excess hydrochloric acid was added and the mixture was hydrolyzed at 100 ° C. for 11 hours to obtain various methoxypolyoxyalkylenediphosphonic acids shown in Table 2.

[0045]

[Table 2]

Production Example 3 3 mol of methoxypolyoxyalkylene glycol (type of AO, average degree of polymerization are as shown in Table 2) and 1 mol of phosphoric anhydride (P ₂ O ₅ ) were placed in a glass reaction vessel. , 80 ° C
The mixture was heated to room temperature and melt-stirred at this temperature for 24 hours to obtain various products shown in Table 3. The end point of the reaction was confirmed by multi-step acid number titration.

[0047]

[Table 3]

The components shown in Table 4 below were used as the component (B). In Table 4, Mw is a weight average molecular weight. In addition,
To the copolymer as the component (B), 0.5% by weight (based on the solid content of the copolymer) of a fatty acid ester-based defoaming agent (Formrex 797, Nika Kagaku) was added.

[0049]

[Table 4]

Incidentally, b-7 was obtained by the following Production Example 4.

Production Example 4 (1) Monomer The following monomers were used as monomers, and the following production method was used.
A copolymer mixture was prepared. A-1: methoxypolyethylene glycol monomethacrylate (EOp = 9, weight average molecular weight 496) A-2: methoxypolyethylene glycol monomethacrylate (EOp = 120, weight average molecular weight 5380) B-1: methacrylic acid (2) Production of Copolymer Mixture 1107 parts by weight of water was charged into a glass reaction vessel, and the temperature was raised to 70 ° C. under a nitrogen atmosphere. Next, the monomer A-1 is added to 1
79 parts by weight, 343 parts by weight of monomer A-2, monomer B-
101 parts by weight, 1 part by weight and 281 parts by weight of water were mixed with the monomer mixture (1), 10% -2-mercaptoethanol aqueous solution 41.0 parts by weight and 10% -ammonium persulfate aqueous solution 3
6.5 parts by weight of 3 liquids were dropped at the same time for 55 minutes to carry out a copolymerization reaction, and then 76 parts by weight of monomer A-1 and 124 parts by weight of monomer A-2 were added to this reaction system. Body B-1 to 2
5.7 parts by weight of water, 103 parts by weight of water and a mixed monomer solution (2) and 10% -2-mercaptoethanol aqueous solution 1
2.0 parts by weight and 10% ammonium persulfate aqueous solution 1
Copolymerization reaction was carried out by simultaneously dropping 0.8 parts by weight of the three liquids for 20 minutes, and further 62 parts by weight of the monomer A-1 and the monomer A-.
2 94 parts by weight, monomer B-1 15 parts by weight, water 78
3 parts by weight of the mixed monomer mixture (3), 18 parts by weight of 10% -2-mercaptoethanol aqueous solution and 7.2 parts by weight of 10% -ammonium persulfate aqueous solution were simultaneously added dropwise for 15 minutes to carry out a copolymerization reaction. The reaction was performed for 90 minutes in total. After completion of the dropping, the mixture was aged at the same temperature for 1 hour, 27.3 parts by weight of 10% ammonium persulfate aqueous solution was added dropwise over 10 minutes, and then aged at 70 ° C. for 2 hours to complete the polymerization reaction. Further, 59 parts by weight of a 48% aqueous sodium hydroxide solution was added for neutralization to obtain a copolymer mixture.

Example A mixture was prepared using the components (A) shown in Tables 1 to 3 and the component (B) shown in Table 4, and the following tests were conducted.

(1) Concrete mix W = 320 g (tap water) C = 800 g (normal Portland cement, specific gravity = 3.
16) S = 1500 g (Kimitsu hill sand) W / C = 40%.

(2) Evaluation item (2-1) Using a viscous mortar mixer, the above-mentioned blending components were kneaded (6
3 rpm, 120 seconds) to prepare concrete. At that time, the amount of the mixture was adjusted so that the mortar flow was 220 mm. Mortar obtained by separating coarse aggregate from this concrete with a sieve having an opening of 5 mm was filled in a device having a shape shown in FIG. 1 manufactured by processing stainless steel (SUS304) with the lower discharge opening closed. After scraping off with the surface of the upper charging opening, let the mortar flow down naturally by opening the lower discharging opening, and the time until holes are confirmed in at least part of the mortar when visually observed from the upper charging opening (downflowing). Time) was measured and used for evaluation of viscosity. The shorter the running time, the lower the viscosity of concrete.

(2-2) Retention Ratio In the above (2-1), the mortar flow value (F ₉₀ ) 90 minutes after the start of mortar kneading was measured, and the percentage [(F ₉₀ ) with respect to the initial flow value (F ₀ ). / F ₀ ) × 100] to calculate the retention rate (%).

(2-3) Setting time The first hydration exothermic peak time was measured using a calorimeter and used as the setting time.

(3) Judgment Criteria The results of (2) above were judged according to the criteria shown in Table 5 below, and a total score was given for the overall evaluation. The results are shown in Tables 6 and 7. If the overall evaluation score is 12 or more, it indicates that good results have been obtained for all required performances, and if 11 or less, there is a problem with any required performance or insufficient performance. Indicates that there is.

[0058]

[Table 5]

[0059]

[Table 6]

[0060]

[Table 7]

The admixture A of Comparative Example 11 was prepared by the following Production Example 5
It is an admixture composed of a copolymer produced by.

Production Example 5 26 mol of water was charged into a reaction vessel equipped with a stirrer, the atmosphere was replaced with nitrogen while stirring, and the temperature was raised to 75 ° C. in a nitrogen atmosphere. A mixture of 0.05 mol of methoxypolyethylene glycol / methacrylic acid ester (EOp = 130) and 0.95 mol of methyl acrylate mixed and dissolved, 0.05 mol of a 20% ammonium persulfate aqueous solution, and 20% 2-mercaptoethanol. Each of 0.1 mol of the aqueous solution is dropped over 3 hours at the same time. Next, 0.02 mol of a 20% ammonium persulfate aqueous solution is added dropwise over 30 minutes, followed by aging at the same temperature (75 ° C.) for 1 hour. After aging, raise the temperature to 95 ° C for 3
0.2 mol of 5% hydrogen peroxide was added dropwise over 30 minutes, and after aging at the same temperature (95 ° C.) for 2 hours, the molecular weight was 20,000.
A copolymer of

[0063]

EFFECTS OF THE INVENTION According to the admixture of the present invention, it is possible to obtain a hydraulic composition satisfying well-balanced flowability, viscosity, flow retention and retardation.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an apparatus used for measuring a downflow time in Examples.

[Explanation of symbols]

1 ... Upper opening 2 ... Lower discharge opening

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification code FI C08L 71/02 C08L 71/02 // C04B 103: 30 C04B 103: 30 (58) Fields investigated (Int.Cl. ⁷ , DB Name) C04B 24/26 C04B 24/32

Claims (4)

(57) [Claims] 1. A (A) and at least one phosphonic acid group (a1), possess at least one of an average degree of polymerization of 1 to 300 <br/> polyoxyalkylene group (a2), based on (a1)
And the ratio of the number of groups (a2) is (a1) / (a2) ≧ 1
The compound or a salt thereof is, and (B) an average polymerization degree of 20 to
A polymer or copolymer obtained by polymerizing a monomer mixture containing 300 polyoxyalkylene group-containing ethylenically unsaturated monomers is (A) / (B) = 90/10 to 10
Admixture for hydraulic composition, which is contained in a weight ratio of / 90 . 2. A weight ratio of (A) / (B) is (A) /
(B) = 70 / 10-10 / 90 , The admixture for hydraulic compositions according to claim 1. 3. (A) is represented by the following general formulas (a-i) and (a)
-Ii) and selected from compounds represented by (a-iii)
The admixture for hydraulic composition according to claim 1 or 2, which is one or more kinds . [Chemical 1] [In the formula, X: -R, and RO- (AO) _n -R ^a1 - at and at least one embedded image Is. R: hydrogen atom or hydrocarbon group having 1 to 18 carbon atoms AO: oxyalkylene group having 2 to 3 carbon atoms n: average degree of polymerization, ^{1 to} 300 R ^a1 , R ^a2 : may be the same or different, Each charcoal
Alkylene group having a prime number of 1 to 5 m: 1 to 6 p: 0 to 5 M: may be the same or different, each is a hydrogen atom,
Alkali metal, alkaline earth metal, ammonium group or
Mono-, di-, or trialkyl which may be substituted by hydroxyl group
(C2-5) An ammonium group is shown. ] 4. (B) is an ethylenically unsaturated carboxylic acid ester having a polyoxyalkylene group having an average degree of polymerization of 20 to 300 and an alkenyl (having 3 to 30 carbon atoms) having a polyoxyalkylene group having an average degree of polymerization of 20 to 300. 5) One or more monomers (b1) selected from ether, and an ethylenically unsaturated mono- or dicarboxylic acid or salt thereof (b
The admixture for a hydraulic composition according to any one of claims 1 to 3, which is a copolymer (B1) obtained by polymerizing a monomer mixture containing 2).