JPH02190306A - Mold release agent for cement product - Google Patents

Abstract

PURPOSE:To provide an effective water-repellent layer on the surface of mortar or concrete, while mold release characteristics of a form is heightened by a method in which the organopolysiloxane having the siloxane unit to which specified alkyl group and hydrolyzable group are bonded is contained in a mold release agent. CONSTITUTION:A mold release agent contains the organopolysiloxane having the siloxane unit to which the alkyl group with two or more carbon atoms and hydrolyzable salt are bonded. The alkyl group and hydrolyzable group may be bonded to same silicon atom, and also may be bonded to different silicon atom. This alkyl group is preferably the alkyl group with the carbon atoms of 5-10, and definitely is ethyl group or n-propyl group, etc. As the hydrolyzable group, alkoxy group or asyloxy group, etc., is used. Since said material does not almost damage structural material and the oder generated in curing reaction is weak and further the stability for storing is excellent, the alkoxy group is preferable, and further especially methoxy group is preferable due to the suitable curing speed obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a mold release agent for cement products. The present invention relates to a mold release agent for cement products that can provide a surface layer with a uniform surface layer.

Technical Background of the Invention Generally, cement products are obtained by pouring cement into a mold and removing the mold, but when removing the mold from the cement product, it is necessary to improve the N-type property of the cement product. Therefore, mold release agents are used.

In addition, in recent years, a serious problem has arisen in which structures made of cement products such as concrete or mortar deteriorate due to salt water, freezing, carbonation, or alkali aggregate reactions, and various countermeasures are being considered. However, no definitive preventive measures have been found.

The deterioration of cement products as described above is generally thought to occur due to the intrusion of water, salt water, gas, etc. into the cement products. For example, cement products become neutral due to the intrusion of carbon dioxide, oxygen, chloride ions (Cρ
) Or reinforcing materials such as reinforcing bars in cement products may corrode due to the intrusion of moisture. Furthermore, if moisture enters the cement product, the moisture may freeze or cause an alkaline aggregate reaction, resulting in deterioration of the cement product.

In order to solve these problems, conventionally, by applying a water-wetted layer forming liquid such as hydrolyzable organosilane or its partially hydrolyzed condensate, silicone resin, or sodium organosiliconate to the surface of cement products, A water-contact layer made of polyorganosiloxane is formed on or near the surface of cement products.

However, with the method of forming a water contact layer as described above, if the cement product is not sufficiently dry, the water contact layer will be formed only on the very surface of the cement product, and the desired effect will not be achieved. Sometimes there wasn't. For this reason, it is necessary to dry and cure the cement product and then apply the water-containing layer forming liquid several times, which is time-consuming and inefficient. It wasn't good.

On the other hand, as a method for imparting water contact properties to cement products such as lightweight cellular concrete and preventing moisture from entering the cement products, for example, Japanese Patent Application Laid-open No. 58-2252 discloses the use of dimethylpolysiloxane in cement products. JP-A-57-123851 discloses a method of adding dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrodiene polysiloxane, or methylcarboxyl-modified polysiloxane emulsified with an anionic surfactant to cement products. A method of adding is disclosed. Furthermore, JP-A-55-42272 discloses that dimethylpolysiloxane, amino group-containing polysiloxane, olefin-containing polysiloxane,
A method of adding fluorine-containing polysiloxane or alcohol-modified polysiloxane is disclosed in JP-A-55-85.
452 discloses a method of adding methylphenylpolysiloxane and chlorophenylmethylpolysiloxane, and JP-A-55-90460 discloses a method of adding methylsilicone varnish, phenylmethylsilicone varnish, silicone Φ epoxy modified face, silicone・A method of adding an alkyd modified varnish, a silicone/acrylic modified varnish, or a silicone/polyester modified varnish is disclosed, and Japanese Patent Application Laid-Open No. 59-232954
The publication discloses a method of adding an alkyl-modified silicone. Furthermore, JP-A-58-50006 discloses a mortar composition containing an alkyl alkoxysilane compound.

However, the above-mentioned method of blending water-retaining agents such as silicone and modified silicone into cement products produces cement products that have homogeneous water contact, but since the water-retaining agents are contained inside the cement product, However, there was a problem in that the amount of water retention agent used was too large, and it was not always practical in terms of economy.

Purpose of the Invention The present invention aims to solve the problems associated with the prior art as described above, and is capable of improving the releasability of the formwork when demolding a cement product from the formwork. ,
The object of the present invention is to provide a mold release agent for cement products that provides an effective water contact layer to the surface of cement products, particularly mortar or concrete.

Summary of the Invention The mold release agent for cement products according to the present invention is characterized by containing an organopolysiloxane having a siloxane unit to which an alkyl group having two or more carbon atoms and a hydrolyzable group are bonded.

DETAILED DESCRIPTION OF THE INVENTION The mold release agent for cement products according to the present invention will be specifically described below.

The mold release agent for cement products according to the present invention contains an organopolysiloxane having a siloxane unit modified with an alkyl group having two or more carbon atoms and a hydrolyzable group. The alkyl group and the hydrolyzable group may be bonded to the same silicon atom or to different silicon atoms. This alkyl group has 2 or more carbon atoms, preferably 4 to 4 carbon atoms.
12, more preferably 5 to 10 alkyl groups, specifically ethyl group, n-propyl group, isopropyl group, n-butyl group, n-pentyl group, n-hexyl group, n-octane group. Examples include groups.

Examples of the hydrolyzable group include an alkoxy group, an acyloxy group, an amino group, an aminoxy group, an oxime group, a ketoxime group, an amide group, an alkenyloxy group, and a halogen atom. Among these, alkoxy groups are preferred because they have no risk of attacking building materials, have a weak odor generated during the curing reaction, and have good storage stability, and methoxy groups are preferred because they provide an appropriate curing speed. is particularly preferred.

Such alkyl alkoxy-modified polysiloxanes are
5 mol% or more of methyl groups in dimethylpolysiloxane 50
Not more than 5 mol% of the methyl groups of the dimethylpolysiloxane are modified with an alkyl group having 2 or more carbon atoms, preferably 4 to 12, more preferably 5 to 10, and 5 mol% or more of the methyl groups of the dimethylpolysiloxane.
It is preferable that 0 mol% or less is modified with an alkoxy group.

If the modification ratio of the alkyl group is lower than this, sufficient water repellency will not be provided, while if it is higher than this, it will be difficult to transfer the halved material to the surface layer of the cement product.

On the other hand, if the modification ratio of alkoxy groups is lower than this, the reactivity with cement components will be low and durability will be poor, and if it is higher than this, sufficient water repellency will not be obtained.

Specifically, the following compounds are used as such organopolysiloxanes.

In the above organopolysiloxane, the total number of siloxane units in one molecule is preferably 2 to 50, particularly preferably 5 to 30.

In addition to the above-mentioned organopolysiloxanes, the mold release agent for cement products used in the present invention is usually a mold release agent such as machine oil, paraffin oil, grease wax, silicone oil, alkyl-modified silicone oil, or alkyl alkoxysilane. The composition may contain components used in formulations, and may further contain antifoaming agents, thickeners, leveling agents, etc., depending on the case.

When the mold release agent for cement products according to the present invention contains components other than such organopolysiloxane, the organopolysiloxane is contained in the mold release agent for cement products in an amount of 10% by weight.
As mentioned above, it is desirable that the content is preferably 30% by weight or more.

The mold release agent for cement products according to the present invention is used by being applied to the contact surface with cement of a mold for forming a cement product, and when the mold is removed from the mold after curing, the releasability of the mold is improved, Moreover, a water repellent layer is formed on the surface of the cement product, which prevents water, salt water, gas, etc. from entering the cement product.

The mold release agent for cement products according to the present invention is used by applying it to a formwork as described above. A mold made of resin or the like is used, and a spray method, a roller method, a brush coating method, or the like is employed to apply the mold release agent to these molds.

The mold release agent for cement products according to the present invention can be used for concrete,
It is mainly used for cement products such as lightweight cellular concrete, mortar, and cement tiles, but it can also be used for inorganic products such as calcium silicate plates, slate, and steam pipes.

Effects of the Invention By applying the mold release agent for cement products according to the present invention to the formwork,
This makes it easier to remove the formwork from the cement product, and also forms a water contact layer on the surface of the cement product, making it possible to obtain cement products with excellent water resistance, salt water resistance, etc. can.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 50 parts by weight of machine oil #150 and 50 parts by weight of alkyl alkoxy-modified silicone oil (ASO) as shown below
A mold release agent was prepared by uniformly mixing parts by weight.

Next, mix cement and Toyoura standard sand at a ratio of 1:3 (weight ratio), add water, make the flow value 170±5, and mix according to JIS R5201 (Physical test method for cement). A sample mortar was prepared.

ASO: Average molecular weight is 3000 and viscosity is 80cs
t, about 30% of the methyl group of dimethylpolysiloxane
mol% is substituted with normal hexyl group, about 20 mol%
A bottomed mold with dimensions of 40 x 40 x 160 + n was assembled using alkyl alkoxy-modified silicone oil substituted with a methoxy group, and the mold release agent prepared as described above was applied to the inner and bottom surfaces of the mold using a brush for 20 t. /rd, and then cast the above test mortar to create a test molded body.

The sample molded body was made of two layers, and each layer was vibrated at a frequency of 9000 r using a table vibrator with an external vibrator.
It was compacted at p■ for 10 seconds. After molding, it was cured in humid air (20°C, 80% relative humidity) for 1 and 7 days, and then removed from the mold.
Then, it was further cured in a humid air (20° C., 80% relative humidity) for 6 days while being sealed in a polyethylene bag. After that, the upper surface that was not in contact with the formwork was sealed with epoxy resin paint, and dried (at 20°C, 50% relative humidity) until the age of the material reached 7, 14, and 28 days. An evaluation was conducted.

Mold releasability The mold releasability of the thus obtained specimens upon demolding was evaluated by A (excellent), B (good), and C (fair).

Depth of water contact layer Each specimen was split open, water was sprayed on the cross section, and the depth of the water contact layer from the surface was measured using calipers.

The water absorption rate specimen was immersed in water at 20° C. for 48 hours, the weight of the specimen before and after immersion was measured, and the water absorption rate was determined using the following formula.

Cv − [(W − W,)/W,] xlOOCv:
Water absorption rate (%) Weight before immersion (g) Wl: Weight after immersion (g) The specimen was immersed in a 2.5% by weight aqueous sodium chloride solution at 20°C for a certain period of time, and the specimen was measured before and after immersion. The amount of ffi was measured, and the water absorption rate of salt water was determined using the following formula.

C'v-[(W'-W')/W']
Xl00C' v: Salt water absorption rate (%) W': Weight before immersion (g) W'': Weight after immersion (g) ■ After measuring the weight, the specimen was divided into two and υN 1792B
(Concrete-Determinology)
f the Ion ChlorldePenet r
0.1% by weight sodium fluorescein solution and 0.1% by weight sodium fluorescein solution and 0.1% by weight sodium fluorescein solution. IN silver nitrate solution was sprayed and the penetration depth of chloride ions was measured.

The results are shown in Table 1.

Example 2 Same as Example 1 except that the mixing ratio of machine oil and alkyl alkoxy-modified silicone oil (ASO) was 25 parts by weight of machine oil and 75 parts by weight of alkyl alkoxy-modified silicone oil. did.

The results are shown in Table 1.

Example 3 The procedure of Example 1 was repeated except that the mixing ratio of machine oil and alkyl alkoxy-modified silicone oil was 0 parts by weight of machine oil and 100 parts by weight of alkyl alkoxy-modified silicone oil.

The results are shown in Table 1.

Comparative Example 1 The same procedure as Example 1 was carried out except that only machine oil was used instead of the mixture of machine oil and alkyl alkoxy-modified silicone oil.

The results are shown in Table 1.

Claims (1)

[Claims] 1. A mold release agent for cement products containing an organopolysiloxane having a siloxane unit to which an alkyl group having two or more carbon atoms and a hydrolyzable group are bonded.