Mold coating agent with adjusted acid value having function as concrete releasing agent

Abstract

The present invention relates to a form coating agent, which has an adjusted acid value and a function of releasing forms from concrete. The present invention uses a copolymer containing: A) melamine polymer resin; B) polystyrene resin; C) phenol-formalin resin; D) polymethylmethacrylate; E) polyacrylate-based resin; and F) polyvinyl chloride.

Claims

1. A form coating agent having a function of releasing forms from concrete, the form coating agent comprising: a polymer resin containing polymethylmethacrylate; a copolymer resin containing vinyl acetate as a side chain; and a terpolymer containing maleic anhydride as a polar group, wherein the polymer resin has a number average molecular weight ranging from 30,000 to 100,000 Daltons (g/mol).

Description

MODE FOR INVENTION

(1) Hereinafter, detailed description will be made on the features of a concrete form coating/coating agent having an adjusted acid value according to a preferred embodiment of the present invention.

(2) The above-described resins are so-called general-purpose polymer resins which are synthesized as a large number of polymer resins according to the average molecular weight and emerged in the market. However, in order to achieve the object of the present invention, the average molecular weight of the polymer resins is limited. For the purpose of the present invention, the limited average molecular weight of the polymer resins is preferably in the range of 20,000 to 200,000, more preferably 30,000 to 100,000, most preferably 40,000 to 90,000. If the average molecular weight of these resins is lower than the lower limit of the above range, the softening point thereof will decrease, and thus concrete molecules will penetrate the resin surface, thus reducing the form release ability of the resins. If the average molecular weight of these resins is higher than the upper limit of the above range, the softening point will increase, and thus the so-called surface crack phenomenon in that the coated surface is finely cracked will occur. In this case, cement molecules will penetrate into the cracks, and thus the resins cannot exert form release performance. Therefore, an object of the present invention is to prepare a form coating/release polymer resin suitable for the purpose of the present invention, which is any one of the above-mentioned six homopolymer resins, in which the form coating/release polymer resin is synthesized to have a limited molecular weight of 30,000 to 100,000 and is used as a release coating agent which is applied to the form surface. Meanwhile, even when two or three of the above-described six resins are mixed, the mixture shows no significant difference in its performance.

(3) Methods of synthesizing the six polymer resins (A to F) to have a limited molecular weight of 30,000 to 100,000 may be performed by various methods, and even polymer resins synthesized by different methods are within the scope of the polymer resins suitable for the purpose of the present invention.

(4) Meanwhile, when the polymer resin having the above-mentioned limited molecular weight is applied to the concrete-contact surface of forms, it has an excellent effect of releasing the forms after concrete curing, but the number of releases of the forms is very limited. The coated surface of forms used for concrete curing after coating with the release coating agent is heavily contaminated by the concrete, and the coating agent applied to the surface is peeled off, indicating that the forms are difficult to use two or three times.

(5) This will now be described by example of polystyrene. The experimental results revealed that the bonding between the molecules of polystyrene applied to the surface is strong, but the surface of polystyrene reused (two or three times) is readily aged, and particularly, the adhesion between polystyrene and the surface of metal forms is weak. For this reason, according to the present invention, the molecular structure of a copolymer was designed, which has one of the above-described six polymer resins as a main chain structure and also has a side chain, which has good surface weather resistance and can increase the adhesion of the main chain to the metal surface, thereby synthesizing a copolymer having suitable comonomer contents. The following four compounds which are polymerized into the side chains of the copolymers were finally selected through sufficient preliminary experiments: a) ethyl vinyl acetate, b) vinyl acetate, c) ethyl methacrylate, and d) 2-hydroxyethyl methacrylate. However, the melamine resin contained e) propanol or f) butanol as a side chain. Thus, a total of 22 copolymers (see Table 1 below regarding the contents) were each applied to the surface of forms, and then a form release experiment after concrete curing was performed. As a result, the results shown in Table 1 below were obtained. The weight content proportion (molecular weight proportion) of the main chain in each of the 22 copolymers A to F is preferably 60 to 99.5 wt %. The content proportion % described in the specification of the present invention means molecular weight % unless otherwise specified.

(6) Meanwhile, the weight content proportion (molecular weight proportion) of the side chain corresponding to each of a) to d) is preferably 0.5 wt % to 40 wt %. In particular, the weight content proportion of d) 2-hydroxyethyl methacrylate is most preferably 1 to 5 wt %. If it is more than 5 wt %, it will increase the weather resistance, but will increase hydrophilic groups, resulting in a significant decrease in the form release ability.

(7) In addition, the polymer resin obtained by synthesis according to the present invention preferably has a solid content ranging from 10 to 45%, and the remainder other than the solid content is a solvent. If the solid content is higher than the upper limit of the above range, the viscosity will increase, making it very difficult to perform the reaction process.

Example 1 (Homopolymer Resin Coating Agent)

(8) 15 wt % (on a solid basis) of each of the six homopolymer resins shown in Table 1 below was mixed with 30 wt % of methyl ethyl ketone (MEK), 25 wt % of toluene and 30 wt % of cellosolve acetate, thereby preparing 10 kg of each coating agent.

(9) At this time, the mixing is preferably performed at a stirring speed of 20 to 150 RPM and a temperature of 25° C. to 55° C. If the stirring speed (RPM) is excessively high, a problem may arise in that the polymer chain is broken, and if the temperature is excessively high, a problem may arise in that the polymer is further polymerized to produce a polymer having a higher molecular weight.

Example 2 (Copolymer Resin Coating Agent)

(10) 15 wt % (on a solid basis) of each of the 22 copolymer resins shown in Table 1 below was mixed with 30 wt % of methyl ethyl ketone (MEK), 25 wt % of toluene and 30 wt % of cellosolve acetate, thereby preparing 10 kg of each coating agent. Here, the stirring speed and the temperature are as described above in Example 1.

(11) An experiment on the form release ability of the coating agents prepared as described above was performed as follows.

(12) Each of the prepared coating agents was applied on the surface of metal forms by means of a painting roller, and dried in an oven at about 25° C. for about 3 hours. Two sheets of the coated metal (60 cm×30 cm) were fixed to face each other at 5 cm intervals, thereby preparing a set of experimental metal forms. Concrete was poured into the 5 cm space between the experimental metal forms, thereby preparing experimental forms filled with about 5-cm-thick concrete. The concrete poured in the experimental forms was cured at about 23° C. for 48 hours, and then the fixing pins were removed from the experimental forms. Then, the forms were dropped vertically once or twice from a height of about 30 cm, and the extent to which the metal forms were released from the concrete by the dropping impact was defined as a measure of the form release ability. In addition, the extent of concrete contamination of the coated surface of the metal forms was observed visually, and the experiment on the form release ability was repeated until the contamination would reach a predetermined value (the experiment was ended when the area of the contaminated portion of the metal surface exceeded 5%).

(13) Here, when the metal forms were not released even though the dropping was carried out up to four times, it was considered that the form release performance of the coating agent was not exhibited. This experiment was conducted by a research institute in a domestic university, and the results of the experiment are shown in Tables 1 and 2 below.

(14) TABLE-US-00001 TABLE 1 C) D) A) B) Phenol- Polymethyl E) F) Melamine Polystyrene formalin methacrylate polyacrylate Polyvinylchloride (2) (3) (2) (2) (2) (2) e) propanol A-e (5) f) butanol A-f (6) a) ethylvinyl B-a (6) C-a (7) D-a (6) E-a (8) F-a (7) acetate b) vinyl B-b (6) C-b (6) D-b (6) E-b (6) F-b (5) acetate c) ethyl B-c (7) C-c(7) D-c (7) E-c (7) F-c (8) methacrylate d) 2- B-d (8) C-d (7) D-d (7) E-d (6) F-d (8) hydroxyethyl methacrylate The number of form releases is based on the degree to which the forms can be reused without any subsequent action after form release from concrete. (If the area of the contaminated portion of the surface of the metal forms was less than 5%, that is, up to a third-round test for the coating agent, the area of the contaminated portion of the metal surfaced was less than 5% of the total area, and in and after a fourth-round test, if the area of the contaminated portion of the metal surfaced was more than 5% of the total area, the number of form releases (form release performance) was determined to be 3.) In the case of the tested copolymer resins shown in Table 1 above, the weight content proportions of the main chains A to F were 92.5 wt % and 97 wt %, and the weight content proportions of the side chains were 7.5 wt % and 3 wt %. Table 1 above shows the results of testing the form release ability of the coating agent comprising each of the homopolymer resins, and the results of testing the form release ability of the coating agent comprising each of the copolymers, each containing the homopolymer resin as the main chain and the introduced side chain. Here, the weight content proportions of the main chains in the copolymers were 92.5 wt % and 97 wt %, and the weight content proportions of the side chains were 7.5 wt % for a) ethylvinyl acetate and b) vinyl acetate, 3 wt % for c) ethyl methacrylate and d) 2-hydroxyethyl methacrylate, and 7.5 wt % for e) propanol and f) butanol. Under such conditions, a total of 22 copolymers were tested. The numbers in parentheses indicate the number of form releases (form release performance) after concrete curing in the forms to which the release coating agent was applied.

(15) As can be seen from the results in Table 1 above, when the form release experiment was performed using the homopolymer resins (A to F) having an average molecular weight of 30,000 to 100,000, the number of form releases was only 2 to 3. However, when the copolymer resins were used, the number of form releases (the number of uses) was increased to 5 to 8, and this appears to be because the adhesion of the copolymer resins to the metal form surface was enhanced due to the effect of the side chains.

(16) When the adhesion of the above-described copolymers needs to be further enhanced, a small amount of carboxylic acid, dicarboxylic acid or a dicarboxylic acid derivative can be introduced into the main chain structure of each of the copolymers, thereby increasing polar groups in the copolymers, thereby preparing terpolymers having an adjusted acid value of 1.5 to 2.0. These terpolymers may be used as metal form release/coating agents.

(17) However, in some cases, the increased polar groups may result in a decrease in the concrete form release ability. As such polar groups that are introduced into the main chains, a′) maleic acid, b′) maleic anhydride, c′) methyl methacrylic acid and d′) acrylic acid are very useful.

(18) At this time, the weight content proportions of the acids that are introduced to form the terpolymers may be in the range of 0.1 wt % to 15 wt %, thereby adjusting the acid value to 1.5 to 20. However, the polar group was not introduced into the copolymer comprising the melamine resin.

(19) Since the melamine resin and the melamine copolymer have strong hydrophilicity in their molecular structure itself, an experiment that introduces hydrophilicity therein was not performed. Thus, the terpolymers having the carboxylic acid or carboxylic acid derivative introduced therein are a total of 80 terpolymers in consideration of four groups (a′ to d′) introduced into the five copolymers (B to F).

(20) These terpolymers were applied once to the form surface, and a form release experiment was performed after concrete curing. As a result, these terpolymers enabled the forms to be used about 9 to 14 times. It is thought that this result was obtained because the coating agent comprising each terpolymer adhered to the concrete surface due to the increased adhesion of the coating agent to the metal form surface, and thus was not detached from the form surface.

(21) The results of introducing these four polar groups indicated that there was no significant difference in adhesion force between the kinds of polar groups, but there was a difference in performance regarding the number of continuous uses of the polar group-introduced terpolymers (B to F). Table 2 below shows the molecular configurations of the 80 terpolymers and the number of form releases for each terpolymer.

(22) TABLE-US-00002 TABLE 2 D) F) A) B) C) Phenol- Polymethyl E) Polyvinyl Melamine Polystyrene formalin methacrylate Polyacrylate chloride a′) maleic A-e (5) B-a-a′ (10) C-a-a′ (9) D-a-a′ (9) E-a-a′ (9) F-a-a′ (12) acid (no polar B-a-b′ (12) C-a-b′ (10) D-a-b′ (9) E-a-b′ (10) F-a-b′ (11) group B-a-c′ (11) C-a-c′ (9) D-a-c′ (10) E-a-c′ (9) F-a-c′ (13) introduced) B-a-d′ (11) C-a-d′ (9) D-a-d′ (9) E-a-d′ (9) F-a-d′ (12) b′) maleic A-f (6) (no B-b-a′ (9) C-b-a′ (9) D-b-a′ (9) E-b-a′ (10) F-b-a′ (9) anhydride polar group B-b-b′ (10) C-b-b′ (10) D-b-b′ (9) E-b-b′ (9) F-b-b′ (9) introduced) B-b-c′ (10) C-b-c′ (9) D-b-c′ (10) E-b-c′ (10) F-b-c′ (10) B-b-d′ (9) C-b-d′ (10) D-b-d′ (9) E-b-d′ (9) F-b-d′ (9) c′) methyl B-c-a′ (9) C-c-a′ (9) D-c-a′ (10) E-c-a′ (10) F-c-a′ (14) methacrylic B-c-b′ (11) C-c-b′ (9) D-c-b′ (9) E-c-b′ (9) F-c-b′ (13) acid B-c-c′ (10) C-c-c′ (10) D-c-c′ (11) E-c-c′ (9) F-c-c′ (12) B-c-d′ (11) C-c-d′ (9) D-c-d′ (9) E-c-d′ (9) F-c-d′ (12) d′) acrylic B-d-a′ (13) C-d-a′ (11) D-d-a′ (10) E-d-a′ (10) F-d-a′ (13) acid B-d-b′ (12) C-d-b′ (10) D-d-b′ (9) E-d-b′ (9) F-d-b′ (14) B-d-c′ (14) C-d-c′ (11) D-d-c′ (9) E-d-c′ (10) F-d-c′ (12) B-d-d′ (13) C-d-d′ (10) D-d-d′ (10) E-d-d′ (11) F-d-d′ (12)

(23) Table 2 above shows the configuration of the terpolymers having the polar groups introduced therein. For example, [B-a-a′] depicts [polystyrene-ethylvinyl acetate-maleic acid]. The numbers in parentheses indicate the number of form releases (form release performance) after concrete curing in the forms to which the release coating agent was applied.

(24) As shown in Table 2 above, the terpolymer release coating agents used in the form release ability experiment after concrete curing in the present invention were tested in five groups classified based on their main chain. Since the difference in the number of uses was not significantly changed by introduction of the four polar groups, the polar groups were introduced in very small amounts (0.6 wt %). These polar groups function to enhance the adhesion of the terpolymers to the hydrophilic metal surface, and did not greatly influence the form release ability on the concrete-contact surface. Here, the polar groups shown in Table 2 above were introduced in very small amounts (0.6 wt %), the terpolymer resins synthesized while substantially maintaining the contents of the main chains and side chains of the copolymers were used in the experiment.

(25) The difference in the number of uses of the release coating agents prepared as described above is summarized below by the ascending order (the order in which the number of uses is smaller). However, each value regarding the number of uses is the average of three experiments conducted on each of the 80 terpolymers after concrete curing.

(26) B) Four terpolymers containing polystyrene as a main chain (9 to 14);

(27) C) Four terpolymers containing phenol-formalin as a main chain (9 to 11);

(28) E) Four terpolymers containing polyacrylate as a main chain (9 to 11);

(29) D) Four terpolymers containing polymethylmethacrylate as a main chain (9 to 11);

(30) F) Four terpolymers containing polyvinyl chloride as a main chain (9 to 14).

(31) In addition, the polymer resins synthesized to have an adjusted acid value of 1.5 to 20 by introducing only the above-described polar groups without introducing side chains into the homopolymers shown in Table 1 above showed a form release number of 4 to 7, indicating that these polymers have excellent performance.

(32) The above-described copolymerization and the reaction for introducing the polar groups can be performed using conventional polymerization inhibitors at a temperature of about 50 to 90° C. In some cases, in order to eliminate unreacted material, these reactions may also be performed at 120° C. for a short time. In addition, it is possible to prepare a coating agent comprising a mixture of two or more of these terpolymers, which have concrete form release ability similar to that of a single terpolymer.