A Release Agent Composition for Inorganic Construction Materials and Applications Thereof Field of the Invention

The invention relates to an oil-based release agent composition containing polysiloxane (s) used for inorganic construction materials to be demolded in a single use. Background of the Invention

Traditional inorganic construction materials include concrete, artificial stones, bricks, and mortars. With China's rapid construction of public facilities, office buildings and apartments, a great amount of interest has been generated by inor- ganic construction materials. Typically, they are made by casting molding, i.e. injecting inorganic cementitious materials (such as Portland cement, white cement, Tuff cement, Pozzolanic cement and sodium silicate) , fine aggregates (such as sand and gravel) , optional coarse aggregates and other additives, mixed with water, into a mold, and removing the molded articles from the mold after curing. In addition to ever- increasing demand for the yield and performance of inorganic construction materials, more and more importance is attached to the amount of residues adhered to the mold walls, and the marginal integrity, porosity, surface smoothness and surface contamination of the molded articles. The surface morphology of inorganic construction materials affects not only aesthetics but also strength and durability of the molded articles. In order to improve demolding properties and surface morphology of inorganic construction materials, a release agent will be applied, before pouring the matrix, onto the mold walls to pre- vent the casted inorganic construction materials from sticking to the mold and ensure a smooth surface of the molded articles.

Traditional release agent compositions for inorganic construe- tion materials are generally divided into sacrificial and semipermanent releases. In general, factories using sacrificial release agents, compared with those using semi-permanent release agents, tend to be more productive and more effective in demolding .

Compositions based on vegetable oils or mineral oils or modified substances thereof are widely used as sacrificial release agents. For example, in CN101348384A, a concrete release agent mixture is prepared by the addition of a mineral oil and an an- ti-rust agent to a decolored mixture of waste machine oil and edible vegetable oil; in US6811810, cement or concrete release compositions are prepared by using vegetable oil and refined paraffin oil (white oil) together with optional ethanol and fatty acids; CN1021972C discloses an emulsion-type concrete re- lease agent prepared with light petroleum fractions, recycled or waste machine oil, edible vegetable oil soapstock and water; in CN1129633A, a gel-like emulsion-type release agent is prepared by heating a mixture of an industrial waste of mixed high-carbon alcohols, vegetable oil soapstocks and a right amount of lye, to which water and waste machine oil are further added and stirred well; CN104479836A discloses a emulsion-type concrete release agent prepared with a mineral oil, sodium laurate, a coupling agent, emulsifiers and stabilizing agents; and CN103305329B discloses an emulsion-type release agent pre- pared by the addition of emulsifiers and water to a polyethylene glycol (PEG) modified vegetable oil polymer obtained by interesterification . These release agents can enhance the demolding properties of inorganic construction materials in an easy and cost-efficient way, but do little to improve the surface morphology of construction materials and fail to address certain problems in demolding. For example, they are less effective in demolding, cause some inorganic construction materials to adhere to the mold walls, and work poorly in enhancing the smoothness of the molded articles. In the existing technologies, oil-base release agents composed of vegetable oils or mineral oils or modified substances thereof tend to cause serious liquid deposit, resulting in incomplete hydration of raw materials, low marginal strength and reduced marginal integrity of the molded articles; high viscosities of raw construction materials make it difficult to discharge the surface gas, leading to a porous surface; while emulsion-type release agents applied to metal molds tend to cause surface corrosion because of high water content. In the course of construction, the construction material surface color may varies in shade from area to area due to different composition, curing time, ambient conditions, or contamination, which leads to an increased rate of surface contamination of the molded articles.

At present, the use of polysiloxanes as the main component of a metal release agent can improve the properties, e.g. morpholo- gy, of the molded metal articles. WO02081121A2 discloses a composition of a modified silicone oil, a low molecular weight silicone oil and a biodegradable synthetic oil, which can be used on demolding, rolling, extrusion or hot-drawing processes of non-ferrous light metals, and can effectively avoid adher- ence between molding material and mold.

CN103103011B discloses an emulsion- type release agent concentrate for concrete, composed of white oil, paraffin wax or sil- icone oil, a certain amount of emulsifiers and defoamers, which can be used by adding water to formulate an aqueous emulsion. This can improve durability and storage of emulsion-type release agent and reduce costs. EP1134060B1 discloses an emul- sion-type concrete release agent, composed of fatty acids, fatty acid derivatives and a polysiloxane having a chain length of 10-150 Si units and containing side groups, where the side groups of the polysiloxane can be hydrogen or a long-chain al- kyl having 4-50 carbon atoms, and the content of polysiloxane is 0.1-10 wt% based on the oil components of the release agent.

Summary of the Invention

The invention aims to provide an oil-based release agent composition containing polysiloxane (s) for inorganic construction materials. Construction products prepared by using the release agent herein are easy to release and show excellent demolding properties, such as low residues on the mold surface, good marginal integrity, high surface smoothness, and small porosity and surface contamination rate. In addition, the oil-based product can effectively reduce the corrosion of the metal molds for a better mold protection.

The oil-based release agent composition for inorganic construction materials contains one polysiloxane or a combination of more polysiloxanes , wherein the dynamic viscosity of the polysiloxane (s) ranges from 50 to 60,000 mPa.s tested at 25°Cac- cording to DIN 53019.

The release agent composition as mentioned above has water con- tent below 5 wt%.

The release agent composition as mentioned above contains less than or equal to 0.01 wt% of surfactant. The release agent composition as mentioned above contains pol- ysiloxane(s) which is/are linear and can be one or more selected from a group of polydimethylsiloxane, hydroxy- terminated polydimethylsiloxane and methylphenyl polysiloxane , preferably from polydimethylsiloxane and hydroxy- terminated polydimethylsiloxane, and more preferably polydimethylsiloxane.

The release agent composition as mentioned above has a poly- siloxane content of 10-100 wt%, based on the total mass of the release agent composition, preferably 20-100 wt%.

The above-mentioned release agent composition contains one or more mineral oils, refined by cracking and fractionation of pe- troleum, used as diluted agent, whose dynamic viscosity ranges from 1 to 2,000 mPa„ s tested according to DIN 53019. Preference is given to refined waste machine oil, white oil and/or solvent oil, whose dynamic viscosities range from 1 to 1,000 mPa.s tested according to DIN 53019. Greater preference is given to white oil and solvent oil, whose dynamic viscosities range from 1 to 500 mPa.s tested according to DIN 53019.

According to National Catalogue of Hazardous Wastes (2014 draft version) (prepared by Ministry of Environmental Protection of the People's Republic of China, and National Development and

Reform Commission of the People's Republic of China), waste machine oils include: engine oil, brake oil, automatic transmission oil, gear oil and other waste lubricants as a result of vehicle and mechanical maintenance; waste refrigerator oils as a result of maintenance and replacement of refrigerators and compressors; waste anti-rust oils used for rust prevention on the surface of castings; waste hydraulic oils as a result of the maintenance and replacement of hydraulic equipments; and waster transformer oils as a result of the maintenance and replacement of transformers.

The release agent composition as mentioned above has a viscosi- ty of from 5 to 5,000 mPa.s tested at 25°C according to DIN 53019.

The release agent composition as mentioned above can be used for the demolding of inorganic construction materials, wherein the inorganic construction materials are mortars, concretes (including cast-in-situs, precast and fiber-reinforced concretes) , and lightweight cementitious products (including aerated concretes and foamed concrete blocks) , and the preferred inorganic construction materials are mortars or concretes .

The invention also provide the use of the release agent composition containing polysiloxane ( s) in the demolding of inorganic construction materials, wherein the release agent composition has water content below 5 wt% and contains less than or equal to 0.01 wt% of surfactant, and the dynamic viscosity of the polysiloxane (s) ranges from 50 to 60,000 mPa.s tested at 25 °C according to DIN 53019.

As in the application as mentioned above, the release agent composition has a viscosity of from 5 to 5,000 mPa.s tested at 25°C according to DIN 53019.

As in the application as mentioned above, the inorganic construction materials are mortars, concretes (including cast-in- situs, precast and fiber-reinforced concretes) , or lightweight cementitious products (including aerated concretes and foamed concrete blocks) , and the preferred inorganic construction materials are mortars or concretes . As in the application as mentioned above, the release agent composition can be used for various types of molds, such as wooden molds, metal molds and plastic molds, preferably for metal molds and particularly preferably for steel or aluminum molds. Its composition has a very low water content, which can reduce the corrosion of metal molds and thus extends their service life. As in the application as mentioned above, the specific weight of the release agent composition applied to molds is between 30 and 100g/m ² , preferably between 40 and 90g/m ² .

As in the application as mentioned above, the drying time, starting from covering the surface of a mold with the release agent composition to pouring the inorganic construction material into the mold, is less than or equal to 30 minutes, preferably 10-20 minutes. The release agent composition herein is described in the following embodiments.

Detailed Description of the Preferred Embodiments

The polysiloxane (s) used in the invention is/are linear and can be one, or a combination, of methyl polysiloxane, hydroxy- terminated polydimethylsiloxane and methylphenyl polysiloxane.

These polysiloxanes are an odorless, colorless or light yellow liquid, having a dynamic viscosity of from 50 to 60,000 mPa . s tested at 25°C according to DIN 53019.

Raw materials used in the invention are as follows: Polydimethylsiloxane 1, linear, by Wacker Chemicals, having a dynamic viscosity of 100 mPa.s tested at 25 °C according to DIN 53019.

Polydimethylsiloxane 2, linear, by Wacker Chemicals, having dynamic viscosity of 1,000 mPa . s tested at 25°C according t< DIN 53019.

Polydimethylsiloxane 3, linear, by Wacker Chemicals, having dynamic viscosity of 2,000 mPa.s tested at 25°C according ti DIN 53019.

Polydimethylsiloxane 4, linear, by Wacker Chemicals, having dynamic viscosity of 5,000 mPa.s tested at 25°C according t< DIN 53019.

Polydimethylsiloxane 5, linear, by Wacker Chemicals, having a dynamic viscosity of 12,500 mPa . s tested at 25°C according to DIN 53019.

Polydimethylsiloxane 6, linear, by Wacker Chemicals, having a dynamic viscosity of 60,000 mPa . s tested at 25°C according to DIN 53019. Hydroxyl-terminated polydimethylsiloxane, linear, by Wacker Chemicals, having a dynamic viscosity of 68 mPa.s tested at 25°C according to DIN 53019, whose molecular chain is terminated at each end by a hydroxyl functional group. Methylphenyl polysiloxane , linear, trade name WACKER ^® AP 1000, by Wacker Chemicals, having a structure at least containing a high proportion of phenyls as side groups and a dynamic viscosity of 1,100 mPa.s tested at 25°C according to DIN 53019. D40, dearomatized solvent oil (SHELLSOL D40 by Shell), having a dynamic viscosity of 1 mPa.s tested at 25 °C according to

DIN53019.

Refined waste machine oil, purchased from Shanghai Inos Build ing Materials Co., Ltd., having a dynamic viscosity of 469 mPa.s tested at 25°C according to DIN 53019.

White oil, purchased from Jiangsu Gaoke Petrochemical Co., Ltd., having a dynamic viscosity of 8 mPa.s tested at 25°C ac cording to DIN 53019.

Table 1

C.

Ex. Ex. Ex. Ex. Ex. Ex.

Composition / wt% Ex.

1 2 3 4 5 6

1

Polydimethylsiloxane 1

67

100 mPa.s

Polydimethylsiloxane 2

100

1,000 mPa. s

Polydimethylsiloxane 3

20

2,000 mPa.s

Polydimethylsiloxane 4

33

5,000 mPa.s

Polydimethylsiloxane 5

10

12,500 mPa.s

Polydimethylsiloxane 6

50

60,000 mPa. s

Hydroxyl-terminated polydimethylsiloxane 100

68 mPa.s

Methylphenylpolysiloxanes 40 1,100 mPa.s

D40

80

1 mPa . s

Refined waste machine oil

50 100 469 mPa.s

White oil

50 8 mPa . s

Viscosity of release agent

composition 1000 760 68 463 7 178 469 mPa . s

Specific coating weight of

release agent composition 90 90 90 90 80 60 90 g/m ²

The application of the release agent composition herein in demolding is embodied as follows:

The release agent compositions for inorganic construction materials of Examples 1-6 and Comparative Example 1 were mixed well and then brushed onto the surfaces of a clean, assembled steel mold with an internal dimension of 10x10x10 cm ³ at a specific coating weight of 60-90 g/m ² . After a waiting time for 10-20 minutes when the release agent compositions were completely- spread on the mold surface, the mortars (mixed in a ratio of Portland cement 42.5: standard sand: water = 1 : 2.5 : 0.5) were poured into the mold, well tamped and cured at room temperature for 24 hours before demolded to obtain a 10x10x10 cm ³ cube specimen. To evaluate the difference in the demolding properties of the compositions in the examples and the comparative example, amount of mortar residues adhered to the inner mold walls, and marginal integrity, porosity, surface smoothness and surface contamination rate of the molded articles were rated as follows: Amount of residues: 24 hours after demolding, the mortar residues adhered to the five inner mold walls (except the top) were removed with a spatula and the amount of residues was calculat- ed. Amount of residues greater than 5.0 g/m ² was given 1 point; amount of residues between 1.0-5.0 g/m ² was given 3 points; and amount of residues less than 1.0 g/m ² was given 5 points.

Marginal integrity: 24 hours after demolding, all 8 edges on the sides and the bottom of a specimen were examined for damage and integrity, and the number of intact edges was recorded. Number of intact edges less than 4 was given 1 point; number of intact edges between 4 and 6 was given 3 points; and number of intact edges greater than 6 was given 5 points .

Porosity: 3 days after demolding, the 4 side surfaces of a specimen were divided into 100 equal squares (i.e. a 10x10 grid) each measured 1x1 cm ² , and the number of areas having pores out of the total number of squares in terms of percentage was recorded. Porosity greater than 50% was given 1 point; porosity between 40% and 50% was given 3 points; and porosity less than 40% was given 5 points.

Surface smoothness: 3 days after demolding, the 4 side surfaces of a specimen were divided into 400 equal squares (i.e. a 20x20 grid) each measured 0.5x0.5 cm ² , and the number of squares that were even and smooth out of the total number of squares in terms of percentage was recorded. Surface smoothness less than 40% was given 1 point; surface smoothness between 40% and 70% was given 3 points; and surface smoothness greater than 70% was given 5 points . Surface contamination rate: 3 days after demolding, the contamination area on the 4 side surfaces of a specimen, caused by the release agent composition, out of the total area of the side surfaces in terms of percentage was recorded. Surface contamination greater than 50% was given 1 point; surface contamination between 20% and 50% was given 3 points; and surface contamination less than 20% was given 5 points.

Based on the above rating criteria, the specimens obtained using the release agent compositions of Examples 1-6 and Comparative Example 1 scored as follows:

Table 2

The compositions of the invention were an oil-based release agent, which can reduce the adhesion of hydrophilic matrix to the inner walls of the mold by forming a hydrophobic release layer on the mold walls. Due to the polysiloxane ( s ) contained in the release agent compositions, not only the porosity on the surface of specimens was significant reduced, but the smoothness of the specimen surfaces was also improved by the defoam- ing effect of the polysiloxane (s) . The release agent compositions in an appropriate range of viscosity could decrease liq- uid deposit, minimizing the impact on the strength of specimen edges . But the experiment discovered that a release agent composition containing polysiloxane ( s ) having a viscosity higher than 60,000 mPa.s was likely to lead to contamination of the specimens.

As can be seen from the scores on porosity of the specimens prepared using the release agents of Examples 1-6 and Comparative Example 1, the polysiloxane (s) contained in the release agent compositions could significantly reduce the number of pores on the surface of the specimens.

As can be seen from the scores on surface contamination rate, the release agent compositions of Examples 1, 3, 5 and 6 scored obviously higher than the release agent composition containing refined waste machine oil of Example 2, which revealed that release agent compositions worked best when they did not contain any diluent or contained white oil and D40 solvent oil as diluent .

Examples 3 and 6 showed that the release agent compositions containing polysiloxane (s) of a relatively low (68 mPa.s) or high (60,000 mPa.s) viscosity exhibited excellent demolding properties .

Examples 1 and 3 to 6 showed that the release agent compositions containing polydimethylsiloxane and hydroxy-terminated polydimethylsiloxane scored relatively high total points with their good demolding properties, wherein the release agent com- position containing polydimethylsiloxane of Example 5 scored the highest total points with its best demolding properties. Examples 1 and 5 showed that the release agent compositions with a viscosity value respectively at the two endpoints (1,000 mPa.s and 7 mPa.s) scored relatively high total points, indicating that the two release agent compositions could still pro- vide excellent demolding properties.