Polyformaldehyde fiber sizing agent for concrete, its preparation method and application

Abstract

The present application provides a kind of polyformaldehyde fiber sizing agent for concrete, including the following mass percentage of ingredients: polyethyleneimine 1.00~15.00%, polyurethane emulsion film forming agent 2.00~30.00%, coupling agent 0.50%~1.50%, PH value regulator 0.01~2.00%, deionized water 51.50%~97.49%.The sizing agent of the present application can modify the surface of polyformaldehyde fiber and enhance the interfacial bonding between the fiber and concrete.The preparation method of the sizing agent is simple, easy to operate, suitable for large-scale industrial production, and the mechanical properties of the modified polyformaldehyde fiber reinforced concrete are significantly improved.The present application also provides a kind of preparation method and application of polyformaldehyde fiber sizing agent for concrete.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a polyformaldehyde fiber sizing agent for concrete, a preparation method and application thereof. BACKGROUND

[0002] Incorporating the reinforcing fiber into cement effectively improves the impermeability, frost resistance and crack resistance of cement concrete, and greatly enhances the impact resistance and shock resistance of cement concrete. Currently, the fibers used for reinforcing and toughening cement concrete mainly include polyamide, carbon fiber, polyester and PP.

[0003] The polyformaldehyde fiber has six characteristics of high strength, high modulus, dimensional stability, good gripping force, good dispersibility and strong alkali resistance, and has excellent physical and mechanical properties and chemical stability. However, the organic POM fiber lacks effective physical and chemical action between the interface of the fiber and inorganic cement concrete, resulting in weak interfacial adhesion strength, and the reinforcing effect of the fiber on the cement concrete is limited. Moreover, the fiber has stable structure and is difficult to modify, so there are few studies on the surface modification of the POM fiber and the interface action between the fiber and concrete. For example, a fiber surface controllable etching method in patent CN201310023040 is modified by using a special process to produce a thread structure production process, and a complex twisting technology is used, which is complex. Patent CN110863347 A uses plasma etching fiber to graft nano-SiO2, but it is difficult to industrialize production due to the limitations of low-pressure plasma requiring a vacuum treatment environment and the low maturity of atmospheric plasma technology. Therefore, it is of great practical significance to find a new method for improving the interface combination between the organic POM fiber and inorganic cement concrete, which is simple to operate, easy to mass produce and good in process. SUMMARY

[0004] The application aims to provide a polyformaldehyde fiber sizing agent for concrete, a preparation method and application thereof. The polyformaldehyde fiber sizing agent in the application has strong bonding strength between the cement concrete.

[0005] The application provides a polyformaldehyde fiber sizing agent for concrete, which comprises the following components in mass fraction:

[0006]

[0007]

[0008] Preferably, the polyethyleneimine has a structure shown in formula I:

[0009]

[0010] In formula I, 1≤n≤700.

[0011] Preferably, the polyurethane emulsion film-forming agent is one or more of a polyester polyurethane emulsion, a polyether polyurethane emulsion, and a polyolefin polyurethane.

[0012] The solid content of the polyurethane emulsion film-forming agent is 40-60%.

[0013] Preferably, the coupling agent is one or more of gamma-methacryloxypropyl trimethoxysilane, gamma-methacryloxypropyl triethoxysilane, and gamma-methacryloxypropyl tri(2-propyl)silane.

[0014] Preferably, the pH regulator is one or more of formic acid, acetic acid, citric acid, and one or more of organic amines.

[0015] The present application provides a method for preparing a polyformaldehyde fiber sizing agent for concrete as described above, comprising the following steps:

[0016] A) mixing polyethyleneimine with 2-4 times the mass of water to obtain a pre-prepared inner layer coating agent;

[0017] B) mixing the polyurethane emulsion film-forming agent with 3-5 times the mass of water, then mixing with the pre-prepared inner layer coating agent to obtain a mixed solution;

[0018] C) mixing the coupling agent and the pH regulator with 40-50% of the total mass of deionized water, stirring until the solution is clear, then mixing with the mixed solution in step B) and making up the remaining deionized water to obtain the polyformaldehyde fiber sizing agent.

[0019] The present application provides the use of the polyformaldehyde fiber sizing agent for concrete as described above in the surface modification of polyformaldehyde fibers.

[0020] The present application provides the use of the polyformaldehyde fiber sizing agent for concrete as described above in improving the bonding strength of polyformaldehyde fibers and concrete.

[0021] Preferably, the concrete is UPHC ultra-high performance concrete.

[0022] The present application provides a polyformaldehyde fiber sizing agent for concrete, comprising the following components in mass percentage: polyethyleneimine 1.00-15.00%, polyurethane emulsion film-forming agent 2.00-30.00%, coupling agent 0.50%-1.50%, pH regulator 0.01-2.00%, and deionized water 51.50%-97.49%. The sizing agent of the present application can modify the surface of polyformaldehyde fibers and enhance the interfacial bonding between the fibers and the concrete. The preparation method of the sizing agent is simple and easy to operate, suitable for large-scale industrial production, and the mechanical properties of the modified polyformaldehyde fiber reinforced concrete are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only the embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of the provided drawings.

[0024] Figure 1 SEM electron microscope picture of polyformaldehyde fiber bare wire in the embodiment 3 of the present application (magnification 650 times);

[0025] Figure 2 SEM electron microscope picture of polyformaldehyde fiber bare wire in the embodiment 3 of the present application (magnification 1000 times);

[0026] Figure 3 SEM electron microscope picture of polyformaldehyde fiber bare wire in the embodiment 3 of the present application (magnification 2000 times);

[0027] Figure 4 SEM electron microscope picture of polyformaldehyde fiber after sizing agent treatment in the embodiment 3 of the present application (magnification 650 times);

[0028] Figure 5 SEM electron microscope picture of polyformaldehyde fiber after sizing agent treatment in the embodiment 3 of the present application (magnification 1000 times);

[0029] Figure 6 SEM electron microscope picture of polyformaldehyde fiber after sizing agent treatment in the embodiment 3 of the present application (magnification 2000 times). DETAILED DESCRIPTION

[0030] The present application provides a polyformaldehyde fiber sizing agent for concrete, which comprises the following components by mass fraction:

[0031]

[0032] Polyformaldehyde is a linear polymer without side chain, high density and high crystallinity, good resistance to organic solvents and chemical stability. The surface of polyformaldehyde fiber has no active groups, and the interface between the fiber and the concrete lacks effective chemical action, the interface action strength is poor, and the fiber itself is stable in structure and difficult to modify. In the present application, polyethyleneimine plays a core bridging role in the sizing agent formula. Some cracks are generated in the polyformaldehyde fiber during the forming process, and the polyethyleneimine as an inner coating agent can fill the gaps of the fiber to produce pinning effect; the amino group contained therein forms hydrogen bond with the C-O bond in polyformaldehyde, thereby enhancing the interface action with the fiber through the two ways of crack filling and hydrogen bond formation, and forming strong mechanical engagement. At the same time, the active functional groups of polyethyleneimine can react with the isocyanate groups in the intermediate emulsion layer

[0033] In the present application, the polyethylene imine has the structure shown in formula I:

[0034]

[0035] In formula I, 1≤n≤700, preferably, 50≤n≤500, more preferably, 100≤n≤400; the weight average molecular weight of the polyethylene imine is preferably 600-25000, more preferably 2000-20000; the mass fraction of the polyethylene imine is preferably 1-15%, more preferably 3-12%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, preferably a range value with any of the above values as the upper limit or lower limit.

[0036] In the present application, the polyurethane emulsion film-forming agent is one of the most important components in the polyformaldehyde fiber sizing agent, which is the intermediate layer of the sizing agent. It determines the process performance and mechanical properties of polyformaldehyde fiber production, processing and composite materials. Selecting a suitable intermediate layer emulsion is conducive to the smoothness of polyformaldehyde fiber in subsequent use, and can also ensure that the polyformaldehyde fiber has the performance of rapid penetration. The water-based polyurethane emulsion has the characteristics of high strength, wear resistance, fatigue resistance and strong bonding force. The hydrogen bond action between the bonded materials can enhance the intramolecular force and make the bonding more firm.

[0037] In the present application, the polyurethane emulsion film-forming agent is preferably a water-based polyurethane emulsion, including one or more of polyester type polyurethane emulsion, polyether type polyurethane emulsion and polyolefin type polyurethane; the solid content of the polyurethane emulsion film-forming agent is preferably 40-60%, more preferably 50%; the mass fraction of the polyurethane emulsion film-forming agent is preferably 2-30%, more preferably 5-25%, such as 2%, 5%, 10%, 15%, 20%, 25%, 30%, preferably a range value with any of the above values as the upper limit or lower limit.

[0038] In the present application, the silane coupling agent is the outermost component in the polyformaldehyde fiber sizing agent, which is a bridging layer connecting the base cement. The silane coupling agent hydrolyzes to produce silanol, and the silanols undergo polycondensation to form a coupling layer on the surface of the cement paste. This coupling layer plays an important role in enhancing the adhesion between the cement paste and the fiber and improving the mechanical properties of the formed composite material.

[0039] In the present application, the coupling agent is preferably a silane coupling agent of methacryloxy group, including one or more of γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane and γ-methacryloxypropyltris(2-propyl)silane; the mass fraction of the coupling agent is preferably 0.5-1.5%, such as 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, preferably a range value with any of the above values as the upper limit or lower limit.

[0040] In the present application, the pH regulator is used to adjust the pH value in the hydrolysis process of the coupling agent, and the pH regulator is preferably one or more of formic acid, acetic acid, citric acid and one or more of organic amines; the mass fraction of the pH regulator is preferably 0.01-2%, more preferably 0.1-1.8%, such as 0.01%, 0.05%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, preferably a range value with any of the above values as the upper limit or lower limit.

[0041] The present application also provides a preparation method of a polyformaldehyde fiber sizing agent for concrete, comprising the following steps:

[0042] A) mixing polyethyleneimine with 2-4 times its mass of water to obtain a pre-prepared inner layer coating agent;

[0043] B) mixing polyurethane emulsion film-forming agent with 3-5 times its mass of water, and then mixing with the pre-prepared inner layer coating agent to obtain a mixed solution;

[0044] C) mixing the coupling agent and the pH regulator with 40-50% of the total mass of deionized water, stirring for hydrolysis, and then mixing with the mixed solution in step B) and supplementing the remaining deionized water to obtain a polyformaldehyde fiber sizing agent.

[0045] In the present application, the stirring speed in the hydrolysis process is preferably 600-700 r / min, more preferably 650 r / min, and the pH value in the hydrolysis process is preferably 3-4, more preferably 3.5.

[0046] The present application also provides the use of the above-mentioned polyformaldehyde fiber sizing agent for concrete in the surface modification of polyformaldehyde fibers, and the oil content on the surface of the polyformaldehyde fibers is preferably 0.5-1.0%.

[0047] After the preparation of the above-mentioned sizing agent is completed, the sizing agent is first diluted to a solid content of 5-6%, and then the polyformaldehyde fiber bare yarn is soaked in the sizing agent and immediately taken out to dry, and then placed in an oven for drying.

[0048] In the present application, the diameter of the polyformaldehyde fiber bare yarn can be 0.2 mm, the temperature of the drying is preferably 100-150 DEG C, more preferably 110-140 DEG C, most preferably 120-130 DEG C, and the time of the drying is preferably 1-10 min, more preferably 3-8 min, most preferably 5-6 min.

[0049] The present application also provides the use of the polyformaldehyde fiber sizing agent for concrete as described above in improving the bonding strength between the polyformaldehyde fiber and the concrete; the concrete is preferably UPHC ultra high performance concrete.

[0050] The present application provides a polyformaldehyde fiber sizing agent for concrete, comprising the following components in mass percentage: polyethyleneimine 1.00-15.00%, polyurethane emulsion film forming agent 2.00-30.00%, coupling agent 0.50%-1.50%, pH value regulator 0.01-2.00%, and deionized water 51.50%-97.49%. The sizing agent can modify the surface of the polyformaldehyde fiber and enhance the interfacial bonding between the fiber and the concrete. The preparation method of the sizing agent is simple and easy to operate, suitable for large-scale industrial production, and the mechanical properties of the polyformaldehyde fiber reinforced concrete after modification are obviously improved.

[0051] In order to further illustrate the present application, the polyformaldehyde fiber sizing agent for concrete, its preparation method and application provided by the present application are described in detail below with examples, but it should not be understood as limiting the protection scope of the present application.

[0052] Example 1

[0053]

[0054] Step 1: dilute the polyethyleneimine with a molecular weight of 10000 with 2 times its mass of water, fully stir to obtain a pre-prepared inner coating agent, and then add it into a preparation container.

[0055] Step 2: dilute the polyether type polyurethane emulsion (model CPIC-CQ-1250) with 3 times its mass of water, fully stir to obtain a pre-prepared inner coating agent, and then add it into a preparation container.

[0056] Step 3: hydrolyze the coupling agent (KH550), add water with a total mass of 40% of the water into the pH value regulator (acetic acid) and the coupling agent in turn, and stir at a speed of 650±50 r / min until the solution is clear.

[0057] Step 4: The coupling agent hydrolysis solution of step 3 is added into the preparation container, and the remaining water is added to make up, and stirred uniformly to obtain the polyformaldehyde fiber sizing agent.

[0058] When used, the sizing agent is diluted with water to about 5% of the total mass of the sizing agent, and then the polyformaldehyde fiber bare yarn with a diameter of 0.2 mm is soaked in the sizing agent, taken out immediately, dried, placed in an oven at 120°C for 5 min, and then taken out. The prepared polyformaldehyde fiber has a surface oil content of 0.6%.

[0059] The cement, sand, water, and the polyformaldehyde fiber prepared above are mixed in a mass ratio of 20:40:10:0.14. The polyformaldehyde fiber is first mixed with the sand and stirred uniformly, and then the cement and water are added in sequence and mixed uniformly to obtain the reinforced cement.

[0060] Example 2

[0061] The sizing agent and polyformaldehyde fiber are prepared according to the method in Example 1, except that the following raw material usage ratio is used instead of the raw material usage ratio of the sizing agent in Example 1:

[0062]

[0063] Example 3

[0064] The sizing agent and polyformaldehyde fiber are prepared according to the method in Example 1, except that the following raw material usage ratio is used instead of the raw material usage ratio of the sizing agent in Example 1:

[0065]

[0066] Comparative Example 1

[0067]

[0068] Step 1: The polyether polyurethane emulsion (CPIC-CQ-1250) is diluted with 3 times its mass of water, and then added into the preparation container after being stirred uniformly.

[0069] Step 2: The coupling agent (KH550) is hydrolyzed. Water with a total mass of 40% of the water is added into the pH adjuster (acetic acid) and the coupling agent in sequence, and stirred at a speed of 650±50 r / min until the solution is clear.

[0070] Step 3: The coupling agent hydrolysis solution of step 3 is added into the preparation container, and the remaining water is added to make up, and stirred uniformly to obtain the polyformaldehyde fiber sizing agent.

[0071] The sizing agent is diluted with water to about 5% of the total mass of the sizing agent, and then the polyformaldehyde fiber bare yarn with a diameter of 0.2 mm is immersed in the sizing agent, taken out immediately, dried, placed in an oven at 120°C for 5 minutes, and then taken out. The prepared polyformaldehyde fiber has a surface oil content of 0.6%.

[0072] Comparative Example 2

[0073]

[0074] Step 1: The polyethyleneimine with a molecular weight (approximate) of 10000 is diluted with water in an amount of 2 times the mass of the polyethyleneimine, and then a pre-prepared inner coating agent is obtained by fully stirring and mixing. The pre-prepared inner coating agent is added to a preparation container.

[0075] Step 2: The bisphenol A type epoxy emulsion (CPIC-CQ-625B) is diluted with water in an amount of 3 times the mass of the bisphenol A type epoxy emulsion, and then the preparation container is added after fully stirring and mixing.

[0076] Step 3: The coupling agent (KH550) is hydrolyzed, and water in an amount of 40% of the total mass of the water is sequentially added to the pH adjuster (acetic acid) and the coupling agent, and stirring is performed at a speed of 650±50 r / min until the solution is clear.

[0077] Step 4: The coupling agent hydrolysis solution of Step 3 is added to the preparation container, and the remaining water is supplemented, and then stirring is uniformly performed, and thus a polyformaldehyde fiber sizing agent is obtained.

[0078] The sizing agent is diluted with water to about 5% of the total mass of the sizing agent, and then the polyformaldehyde fiber bare yarn with a diameter of 0.2 mm is immersed in the sizing agent, taken out immediately, dried, placed in an oven at 120°C for 5 minutes, and then taken out. The prepared polyformaldehyde fiber has a surface oil content of 0.6%.

[0079] The polyformaldehyde fiber prepared in Example 3 and the untreated polyformaldehyde fiber raw yarn are observed and analyzed by a Phenom desktop scanning electron microscope for the micro-morphology of the polyformaldehyde fiber before and after modification. The contact angle and the interface performance are tested by a contact angle method and a pull-out method, and the bending load of the concrete under different deflections is measured according to the GB / T 50081 concrete flexural strength test method to test the reinforcing performance of the concrete.

[0080] Contact angle test: a water droplet is dropped onto a polyformaldehyde fiber single yarn, and the image of the water droplet is captured by a high-resolution camera, and then the angle is automatically measured by software. Then, diiodomethane and n-hexadecane are respectively dropped onto the polyformaldehyde fiber single yarn to measure the contact angle, and the surface energy is calculated by the contact angles of water, diiodomethane, and n-hexadecane.

[0081] Interface performance test: cement (general portland cement meeting GB175 requirements), sand (Chinese ISO standard sand), water are mixed in proportion of 2:4:1 to make mortar, polyformaldehyde monofilament is inserted into the cement to make monofilament pulling-out test sample, and the interface strength between polyformaldehyde and cement base is tested by using a universal mechanical laboratory.

[0082] Bending load test: 0.2% polyformaldehyde fiber is added to cement mortar and uniformly mixed to make a standard test piece with a side length of 150mmX150mmX600mm or a prism test piece of 150mmX150mmX550mm, and there is no hole with a diameter exceeding 5mm and a depth exceeding 2mm in the middle surface of the test piece in the length direction; the test piece is fixed to the press machine by using a bending clamp and a deflection meter is installed to measure the deformation amount, and the bending load applied to the test piece by the press machine at different deflections is measured by using four-point bending method.

[0083] Table 1 performance test data of examples 1-3

[0084]

[0085] It can be seen from the test data that the contact angle, surface energy and interface strength of the polyformaldehyde fiber after sizing and coating are obviously improved compared with the uncoated fiber, the contact angle of the treated polyformaldehyde fiber with water gradually decreases, the surface energy gradually increases, and the greater the surface energy, the better the wettability. In example 3, the contact angle with water is reduced by 43.6%, the surface energy is increased by 15.3%, and the interface strength is increased by 48.9%, which shows that the combination of the sized polyformaldehyde fiber with the cement base will be obviously improved, and the improvement of the polyformaldehyde fiber reinforced ultra-high performance concrete mid-span deflection test result also proves this point.

[0086] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A polyformaldehyde fiber sizing agent for concrete, comprising the following components by mass fraction: polyethyleneimine 5.00~15.00% polyurethane emulsion film former 2.00~30.00% coupling agent 0.50%~1.50% pH value regulator 0.01~1.00% deionized water 51.50%~97.49%; the polyethyleneimine has the structure shown in formula I: Formula I; in formula I, 1≤n≤700.

2. The polyformaldehyde fiber sizing agent for concrete according to claim 1, characterized by, the polyurethane emulsion film former is one or more of polyester type polyurethane emulsion, polyether type polyurethane emulsion and polyolefin type polyurethane emulsion; the solid content of the polyurethane emulsion film former is 40~60%.

3. The polyformaldehyde fiber sizing agent for concrete according to claim 1, characterized by, the coupling agent is one or more of γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropyltriethoxysilane and γ-methacryloyloxypropyltri(2-propyl)silane.

4. The polyformaldehyde fiber sizing agent for concrete according to claim 1, characterized by, the pH value regulator is one or more of formic acid, acetic acid, citric acid and organic amine. 5.A method for preparing the polyformaldehyde fiber sizing agent for concrete according to any one of claims 1~4, comprising the following steps: A) mixing polyethyleneimine with 2~4 times the mass of water to obtain a pre-prepared inner layer coating agent; B) mixing polyurethane emulsion film former with 3~5 times the mass of water, then mixing with the pre-prepared inner layer coating agent to obtain a mixed solution; C) mixing the coupling agent and the pH value regulator with 40~50% of the total mass of deionized water, stirring until the solution is clear, then mixing with the mixed solution in step B) and making up the remaining deionized water to obtain the polyformaldehyde fiber sizing agent. 6.The use of the polyformaldehyde fiber sizing agent for concrete according to any one of claims 1~4 in the surface modification of polyformaldehyde fibers. 7.The use of the polyformaldehyde fiber sizing agent for concrete according to any one of claims 1~4 in improving the bonding strength of polyformaldehyde fibers and concrete.

8. Use according to claim 7, characterized in that, the concrete is UPHC ultra-high performance concrete.

Images