A method for producing a hydrophilically modified polypropylene fiber reinforced concrete material

Abstract

The application discloses a preparation method of hydrophilic modified polypropylene fiber reinforced coagulation material. The preparation method of the hydrophilic modified polypropylene fiber is as follows: firstly, polypropylene is grafted with resin acid through gamma ray irradiation; then, the grafted polypropylene is melt-mixed with polypropylene at a certain proportion; the mixture is extruded through a spinneret, cooled in a water bath, pulled up and finally heat-set and cut to obtain the hydrophilic modified polypropylene fiber. The obtained hydrophilic modified polypropylene fiber is mixed with cement, aggregate, high-efficiency water reducing agent and water at a certain proportion to prepare the hydrophilic modified polypropylene fiber reinforced concrete material. The method uses natural raw material resin acid to modify the polypropylene, and belongs to a green modification method; and the impact strength, bending toughness and surface smoothness of the finally prepared concrete material are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, specifically to a hydrophilic modified polypropylene fiber reinforced concrete material and its preparation method. Background Technology

[0002] Concrete's raw materials are extremely common and abundant in nature, readily available and inexpensive. Before setting, concrete can be shaped into any form according to the mold, adapting to various uses. It can be formulated into concrete of various strengths as needed, and its performance can be tailored to specific applications through adjustments to its mix design and manufacturing process. Concrete is durable, requires little maintenance, and is highly adaptable to the influence of natural conditions. However, concrete's inherent drawbacks, such as its heavy weight, low tensile strength, brittleness, poor impact and abrasion resistance, and susceptibility to plastic cracking, make it difficult to meet the requirements of certain engineering projects. When concrete cracks exceed certain limits, they accelerate material aging and structural deterioration, leading to a reduction in structural load-bearing capacity and durability.

[0003] Composite materials are a major approach to achieving high performance in cement-based materials, and fiber reinforcement is one of the key methods. The incorporation of fibers can inhibit the formation and delay the development of concrete cracks under load, effectively improve the concrete's resistance to chloride ion penetration, and enhance its durability. Polypropylene (PP) fibers are ideal for meeting the requirements of reinforcement and toughening. PP fibers have many advantages, such as a high melting point, 100% wet strength retention, light weight, low price, and excellent processing performance, especially exhibiting remarkable stability in alkaline environments. The incorporation of PP fibers can inhibit the formation and development of fine cracks on and within the concrete surface, reducing tensile stress concentration caused by repeated freeze-thaw cycles. This process both inhibits crack initiation and limits expansion caused by freezing, effectively improving the concrete's freeze-thaw resistance and impermeability, thus enhancing the durability of the concrete structure. However, due to the low dispersibility and hydrophobic surface of ordinary PP fibers, the surface interaction force after mixing with concrete is weak. Therefore, improving the bond between PP fibers and the cement matrix is ​​the most important and crucial issue in the research of PP fiber application in cement reinforcement. Because in the fiber-cement dispersion phase, the stress on the fiber is transmitted through the fiber-matrix interface. If the interfacial adhesion is weak, the fiber will separate from the concrete before the fiber reaches its maximum tensile strength, and the desired reinforcement effect will not be obtained. Therefore, the surface of polypropylene fiber must be modified to make it hydrophilic and enhance the adhesion between the fiber and the matrix.

[0004] Resin acid (molecular formula C) 19 H 29(COOH) is the main component of rosin, accounting for 85-90% of its total mass. Rosin can be considered a melt of various isomers of resin acids. Resin acid molecules can be viewed as monocarboxylic acids containing two double bonds and a tricyclic phenanthrene skeleton. Based on the different positions of the double bonds and the different configurations of the hydrocarbon groups attached to C-13, resin acids can be classified into abietic acid type, piratic acid type, etc., as shown in the structural formula below:

[0005]

[0006] Resin acid molecules possess two chemical reaction centers: a double bond and a carboxyl group. The carboxyl group (COO) in resin acid molecules... - It can react with Ca in cement paste. 2+ Due to ion complexation, various resin acid molecules have been widely used in the concrete industry, such as resin acid air-entraining agents and resin acid water-reducing agents. Their preparation methods are simple and inexpensive.

[0007] Accordingly, this invention uses gamma ray irradiation to graft resin acid onto polypropylene through double bonds in its molecules. At the same time, the carboxyl groups in the resin acid can improve the hydrophilicity of polypropylene, thereby preparing a hydrophilic modified polypropylene fiber reinforced concrete material with excellent bonding ability between polypropylene fibers and concrete matrix. Summary of the Invention

[0008] This invention provides a method for preparing resin-acid-grafted hydrophilically modified polypropylene fibers and resin-acid-grafted hydrophilically modified polypropylene fiber-reinforced concrete materials by gamma-ray irradiation grafting. When resin-acid-grafted hydrophilically modified polypropylene fibers are used to reinforce concrete, the presence of carboxyl hydrophilic groups on the fiber surface allows for chemical interfacial bonding with the concrete, significantly improving the interfacial bond strength between the polypropylene fiber and the concrete. Due to this substantial increase in fiber-concrete interfacial bond strength, the fibers in the concrete are no longer pulled out but rather broken, thus fully developing and utilizing the tensile strength of the fibers, thereby greatly enhancing the reinforcing effect of the fibers.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A novel hydrophilic modified polypropylene fiber reinforced concrete material is disclosed. The concrete mainly comprises the following components: hydrophilic modified polypropylene fibers, cement, aggregates, a high-efficiency water-reducing agent, and water. The preparation method of the hydrophilic modified polypropylene fiber reinforced concrete material is as follows: First, the aggregates, cement, and high-efficiency water-reducing agent of the specified weight components are placed in a forced mixer. Then, the polypropylene fibers of the specified weight component are dispersed and added to the mixer. The aggregates, cement, high-efficiency water-reducing agent, and polypropylene fibers are first dry-mixed for about 3 minutes, and then water is added and wet-mixed for another 3 minutes to obtain the hydrophilic modified polypropylene fiber reinforced concrete material.

[0011] Furthermore, the hydrophilic modified polypropylene fiber mainly comprises the following components: polypropylene resin raw material and modified filler weighing 10% to 40% of the polypropylene mass, which are prepared by melt blending, stretching, and shaping.

[0012] Furthermore, the method for preparing hydrophilic modified polypropylene fiber includes the following steps: At a certain temperature, polypropylene and modified filler are mixed in a certain proportion and then placed in the hopper of an extruder for melt extrusion. After extrusion through the spinneret of the extruder, the mixture is cooled in a water bath at a certain temperature (10–30°C). The resulting fiber is then drawn a certain multiple (6–10 times) at a certain temperature (100–140°C), and then heat-set at 80–110°C (to eliminate internal stress generated during forced stretching). Finally, the resulting fiber undergoes post-treatment and is cut.

[0013] The extruder described in this invention is a twin-screw extruder, and the extrusion molding temperature is as follows: feeding section 160-170℃, plasticizing section 220-235℃, homogenizing section 240-250℃, and die spinneret temperature 280-300℃.

[0014] The polypropylene described in this invention is a homopolymer polypropylene with an isotacticity greater than 95% and a melt flow index (MFR) of less than 2 g / 10 min under a load of 2.16 kg and a temperature of 180 °C.

[0015] The modified filler described in this invention is resin acid-grafted polypropylene fiber. Resin acid-grafted polypropylene fiber can improve the hydrophilicity of polypropylene fiber and improve the dispersibility of polypropylene fiber in concrete.

[0016] The resin acid used in this invention is preferably rosin, produced by Jiangxi Songtai Chemical Plant, and is an industrial grade 1 product.

[0017] The method for preparing resin acid grafted polypropylene fiber according to the present invention is as follows: 1-9 parts by weight of resin acid are dissolved in ethanol and mixed with 100 parts by weight of polypropylene in a high-speed mixer. After the ethanol has completely evaporated, the mixture is extruded and granulated in a twin-screw extruder. The resulting particles are then grafted by irradiation to obtain resin acid grafted polypropylene with a grafting rate of 1-9 wt% and a gel content of less than 5 wt%.

[0018] The irradiation source used in the irradiation grafting reaction of resin acid-grafted polypropylene is 60 The cobalt source has an irradiation dose of 1–50 kGy, preferably 15–45 kGy.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) This method uses 60 Co-ray irradiation generates free radicals that react with the double bonds in the resin acid. Instead of using conventional benzoyl peroxide (DCP) to generate free radicals, this avoids the crosslinking of PP by free radicals generated by DCP.

[0021] (2) Due to the use of bio-based material resin acid, this method is a green grafting modification method for polypropylene. Attached Figure Description

[0022] Figure 1 Infrared spectrum of the resin-grafted polypropylene prepared in Example 1;

[0023] Figure 2 Infrared spectrum of the resin-grafted polypropylene prepared in Example 2;

[0024] Figure 3 Infrared spectrum of the resin-grafted polypropylene prepared in Example 3;

[0025] Figure 4 Infrared spectrum of the resin-grafted polypropylene prepared in Example 4;

[0026] Figure 5 Infrared spectrum of the resin-grafted polypropylene prepared in Example 5. Detailed Implementation

[0027] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0028] In the following examples, unless otherwise specified, all reagents used are existing products.

[0029] Example 1

[0030] Step 1: First, dissolve 1 part by weight of rosin in ethanol, then mix it with 100 parts by weight of 95% isotactic polypropylene with a melt flow index (MFR) of 0.8 g / 10 min in a high-speed mixer at a ratio of 100 / 1 (polypropylene / rosin, wt / wt). After the ethanol has completely evaporated, feed it into the feeding hopper of a twin-screw extruder. Control the extrusion melt temperature at 180℃, cool it in a water bath and granulate it to obtain polypropylene + rosin mixture granules for later use.

[0031] Step Two: Place the polypropylene + rosin mixture granules from Step One into a polyethylene plastic bag, seal it using a vacuum sealer, and then irradiate it with a cobalt source at room temperature using 15 kGy Gama rays. Afterward, wash it three times with ethanol to remove a small amount of ungrafted rosin, thus obtaining resin-grafted polypropylene fiber (PP-1rosin). The infrared spectrum is shown below. Figure 1 As shown in the figure, compared with the pure PP (PP-0roisn) spectrum, the PP-1rosin spectrum can be seen at 1735 cm⁻¹. -1 The infrared characteristic peak of carbonyl groups in rosin was observed, proving that the resin acid irradiation grafting into polypropylene was successful.

[0032] Example 2

[0033] Step 1: First, dissolve 3 parts by weight of rosin in ethanol, then mix it with 100 parts by weight of 95% isotactic polypropylene with a melt flow index (MFR) of 0.8 g / 10 min in a high-speed mixer at a ratio of 100 / 3 (polypropylene / rosin, wt / wt). After the ethanol has completely evaporated, feed it into the feeding funnel of a twin-screw extruder. Control the extrusion melt temperature at 190℃, cool it in a water bath and granulate it to obtain polypropylene + rosin mixture granules for later use.

[0034] Step Two: Place the polypropylene + rosin mixture granules from Step One into a polyethylene plastic bag, seal it using a vacuum sealer, and then irradiate it with a cobalt source at room temperature using 20 kGy Gama rays. Afterward, wash it three times with ethanol to remove a small amount of ungrafted rosin, thus obtaining resin-acid-grafted polypropylene fiber (PP-3rosin). The infrared spectrum is shown below. Figure 2 As shown in the figure, compared with the pure PP (PP-0rosin) spectrum, the PP-3rosin spectrum can be observed at 1735 cm⁻¹. -1 The presence of infrared characteristic peaks for carbonyl groups in rosin confirms the successful grafting of resin acid into polypropylene via irradiation, while simultaneously... Figure 1 Compared to the previous results, the carbonyl peak is more intense, which proves that the resin has a higher amount of acid grafting.

[0035] Example 3

[0036] Step 1: First, dissolve 5 parts by weight of rosin in ethanol, then mix it with 100 parts by weight of 95% isotactic polypropylene with a melt flow index (MFR) of 0.8 g / 10 min in a high-speed mixer at a ratio of 100 / 5 (polypropylene / rosin, wt / wt). After the ethanol has completely evaporated, feed it into the feeding hopper of a twin-screw extruder. Control the extrusion melt temperature at 200℃, cool it in a water bath and granulate it to obtain polypropylene + rosin mixture granules for later use.

[0037] Step Two: Place the polypropylene + rosin mixture granules from Step One into a polyethylene plastic bag, seal it using a vacuum sealer, and then irradiate it with 25 kGy Gama rays at room temperature in a cobalt source. Afterward, wash it three times with ethanol to remove a small amount of ungrafted rosin, thus obtaining resin-grafted polypropylene fiber (PP-5rosin). The infrared spectrum is shown below. Figure 3 As shown in the figure, compared with the pure PP (PP-0rosin) spectrum, the PP-5rosin spectrum can be observed at 1735 cm⁻¹. -1 The presence of infrared characteristic peaks for carbonyl groups in rosin confirms the successful grafting of resin acid into polypropylene via irradiation, while simultaneously... Figure 2 Compared to the previous results, the intensity of the carbonyl peak was further improved, which proves that the amount of resin acid grafting was also increased accordingly.

[0038] Example 4

[0039] Step 1: First, dissolve 7 parts by weight of rosin in ethanol, then mix it with 100 parts by weight of 95% isotactic polypropylene with a melt flow index (MFR) of 0.8 g / 10 min in a high-speed mixer at a ratio of 100 / 7 (polypropylene / rosin, wt / wt). After the ethanol has completely evaporated, feed it into the feeding hopper of a twin-screw extruder. Control the extrusion melt temperature at 210℃, cool it in a water bath and granulate it to obtain polypropylene + rosin mixture granules for later use.

[0040] Step Two: Place the polypropylene + rosin mixture granules from Step One into a polyethylene plastic bag, seal it using a vacuum sealer, and then irradiate it with a cobalt source at room temperature using 30 kGy Gama rays. Afterward, wash it three times with ethanol to remove a small amount of ungrafted rosin, thus obtaining resin-acid-grafted polypropylene fiber (PP-7rosin). The infrared spectrum is shown below. Figure 4 As shown in the figure, compared with the pure PP (PP-0roisn) spectrum, the PP-7rosin spectrum can be observed at 1735 cm⁻¹. -1 The presence of infrared characteristic peaks for carbonyl groups in rosin confirms the successful grafting of resin acid into polypropylene via irradiation, while simultaneously... Figure 3 Compared to the previous results, the intensity of the carbonyl peak was further improved, which proves that the amount of resin acid grafting was also increased accordingly.

[0041] Example 5

[0042] Step 1: First, dissolve 9 parts by weight of rosin in ethanol, then mix it with 100 parts by weight of 95% isotactic polypropylene with a melt flow index (MFR) of 0.8 g / 10 min in a high-speed mixer at a ratio of 100 / 9 (polypropylene / rosin, wt / wt). After the ethanol has completely evaporated, feed it into the feeding funnel of a twin-screw extruder. Control the extrusion melt temperature at 220℃, cool it in a water bath, and granulate it to obtain polypropylene + rosin mixture granules for later use.

[0043] Step Two: Place the polypropylene + rosin mixture granules from Step One into a polyethylene plastic bag, seal it using a vacuum sealer, and then irradiate it with 45 kGy Gama rays at room temperature in a cobalt source. Afterward, wash it three times with ethanol to remove a small amount of ungrafted rosin, thus obtaining resin-grafted polypropylene fiber (PP-9rosin). The infrared spectrum is shown below. Figure 5 As shown in the figure, compared with the pure PP (PP-9rosin) spectrum, the PP-9rosin spectrum can be seen at 1735 cm⁻¹. -1 The presence of infrared characteristic peaks for carbonyl groups in rosin confirms the successful grafting of resin acid into polypropylene via irradiation, while simultaneously... Figure 4 Compared to the previous results, the intensity of the carbonyl peak is further increased, which proves that the amount of resin acid grafting is also correspondingly increased.

[0044] Example 6

[0045] 100 parts by weight of 95% isotactic polypropylene with a melt flow index (MFR) of 0.8 g / 10 min and 10 wt% of the resin-grafted polypropylene (PP-9rosin) prepared in Example 5 were mixed and then fed into a single-screw extruder via a metering device. The extruded melt temperature was controlled at 230°C. The melt was mixed by a static mixer, filtered, metered by a metering pump, and extruded from a perforated spinneret. The temperatures of each zone of the screw were set as follows:

[0046]

[0047] After being cooled and solidified in a water bath, the resulting fibers are stretched 6.0 times at 100°C using a stretching device, then shaped at 80°C and cut into polypropylene coarse fibers of predetermined length.

[0048] Example 7

[0049] 100 parts by weight of 95% isotactic polypropylene with a melt flow index (MFR) of 0.8 g / 10 min and 30% of the resin-grafted polypropylene (PP-9rosin) prepared in Example 5 were mixed and then fed into a single-screw extruder via a metering device. The extruded melt temperature was controlled at 230°C. The melt was mixed by a static mixer, filtered, metered by a metering pump, and extruded from a perforated spinneret. The temperatures of each zone of the screw were set as follows:

[0050]

[0051] After being cooled and solidified in a water bath, the resulting fibers are stretched 10 times at 140°C using a stretching device, then shaped at 110°C and cut into polypropylene coarse fibers of predetermined length.

[0052] Example 8

[0053] 100 parts by weight of 95% isotactic polypropylene with a melt flow index (MFR) of 0.8 g / 10 min and 40% of the resin-grafted polypropylene (PP-9rosin) prepared in Example 5 were mixed and added to a single-screw extruder via a metering device. The extruded melt temperature was controlled at 230°C. The melt was mixed by a static mixer, filtered, metered by a metering pump, and extruded from a perforated spinneret. The temperatures of each zone of the screw were set as follows:

[0054]

[0055] After being cooled and cured in a water bath, the resulting fibers are stretched six times at 100°C using a stretching device, then shaped at 80°C and cut into polypropylene coarse fibers of predetermined length.

[0056] Example 9

[0057] 100 parts by weight of 95% isotactic polypropylene with a melt flow index (MFR) of 0.8 g / 10 min and 20% of the resin-grafted polypropylene (PP-7rosin) prepared in Example 4 were mixed and added to a single-screw extruder via a metering device. The extruded melt temperature was controlled at 230°C. The melt was mixed by a static mixer, filtered, metered by a metering pump, and extruded from a perforated spinneret. The temperatures of each zone of the screw were set as follows:

[0058]

[0059] After being cooled and solidified in a water bath, the resulting fibers are stretched seven times at 110°C using a stretching device, then shaped at 85°C and cut into coarse polypropylene fibers of a predetermined length.

[0060] Example 10

[0061] 100 parts by weight of 95% isotactic polypropylene with a melt flow index (MFR) of 0.8 g / 10 min and 30% of the resin-grafted polypropylene (PP-7rosin) prepared in Example 4 were mixed and added to a single-screw extruder via a metering device. The extruded melt temperature was controlled at 230°C. The melt was mixed by a static mixer, filtered, metered by a metering pump, and extruded from a perforated spinneret. The temperatures of each zone of the screw were set as follows:

[0062]

[0063] After being cooled and cured in a water bath, the resulting fibers are stretched nine times at 130°C using a stretching device, then shaped at 95°C and cut into coarse polypropylene fibers of a predetermined length.

[0064] Example 6 60 0.6 600 9 15 Example 7 60 0.7 700 11 6 Example 8 55 1.0 550 11 4 Example 9 65 0.6 600 9.5 10 Example 10 60 1.0 700 12 8

[0065] Example 11

[0066] In Example 6, the composition is 1.2 parts polypropylene fiber, 300 parts cement, 750 parts aggregate, 1.6 parts high-efficiency water-reducing agent, and 150 parts water. First, the aggregate, cement, and high-efficiency water-reducing agent are placed in a mixer and mixed evenly. Then, the polypropylene fiber is dispersed and added, and the mixture is dry-mixed for 3 minutes, followed by wet-mixing with water for another 3 minutes to obtain the polypropylene fiber concrete.

[0067] Example 12

[0068] In Example 7, the composition is 1.2 parts polypropylene fiber, 300 parts cement, 750 parts aggregate, 1.6 parts high-efficiency water-reducing agent, and 150 parts water. First, the aggregate, cement, and high-efficiency water-reducing agent are mixed evenly in a mixer. Then, the polypropylene fiber is dispersed and added, and the mixture is dry-mixed for 3 minutes. Next, water is added and the mixture is wet-mixed for 3 minutes to obtain the polypropylene fiber concrete.

[0069] Example 13

[0070] In Example 8, the composition is 1.2 parts polypropylene fiber, 300 parts cement, 750 parts aggregate, 1.6 parts high-efficiency water-reducing agent, and 150 parts water. First, the aggregate, cement, and high-efficiency water-reducing agent are placed in a mixer and mixed evenly. Then, the polypropylene fiber is dispersed and added, and the mixture is dry-mixed for 3 minutes. Next, water is added and the mixture is wet-mixed for 3 minutes to obtain the polypropylene fiber concrete.

[0071] Example 14

[0072] In Example 9, the composition is 1.2 parts polypropylene fiber, 300 parts cement, 750 parts aggregate, 1.6 parts high-efficiency water-reducing agent, and 150 parts water. First, the aggregate, cement, and high-efficiency water-reducing agent are mixed evenly in a mixer. Then, the polypropylene fiber is dispersed and added, and the mixture is dry-mixed for 3 minutes. Next, water is added and the mixture is wet-mixed for 3 minutes to obtain the polypropylene fiber concrete.

[0073] Example 15

[0074] In Example 10, the composition is 1.2 parts polypropylene fiber, 300 parts cement, 750 parts aggregate, 1.6 parts high-efficiency water-reducing agent, and 150 parts water. First, the aggregate, cement, and high-efficiency water-reducing agent are placed in a mixer and mixed evenly. Then, the polypropylene fiber is dispersed and added, and the mixture is dry-mixed for 3 minutes. Next, water is added and the mixture is wet-mixed for 3 minutes to obtain the polypropylene fiber concrete.

[0075] Comparative Example 1

[0076] The mixture consists of 1.2 parts unmodified polypropylene fiber, 300 parts cement, 750 parts aggregate, 1.6 parts high-efficiency water-reducing agent, and 150 parts water. First, the aggregate, cement, and high-efficiency water-reducing agent are mixed evenly in a mixer. Then, the polypropylene fiber is dispersed and added, and the mixture is dry-mixed for 3 minutes. Next, water is added and the mixture is wet-mixed for 3 minutes to obtain the polypropylene fiber concrete.

[0077]

[0078]

[0079]

Claims

1. A hydrophilic modified polypropylene fiber reinforced concrete material, characterized in that, The concrete comprises the following components: hydrophilic modified polypropylene fiber, cement, aggregate, high-efficiency water-reducing agent, and water. The concrete material is prepared by mixing 300 parts cement, 700 parts aggregate, and 1.6 parts high-efficiency water-reducing agent evenly, then adding 1.2 parts hydrophilic modified polypropylene fiber and mixing further, finally adding 150-160 parts water and mixing thoroughly to obtain the hydrophilic modified polypropylene fiber reinforced concrete material. The hydrophilic modified polypropylene fiber is obtained by mixing polypropylene with a polypropylene mass fraction of 10-40 wt%. The resin acid-modified polypropylene is obtained by melting and mixing 1-9 parts by weight of resin acid in ethanol, mixing it with 100 parts by weight of polypropylene in a high-speed mixer, and after the ethanol has completely evaporated, extruding and granulating it in a twin-screw extruder. The resulting particles are then grafted by irradiation to obtain resin acid-modified polypropylene with a grafting rate of 1-9 wt% and a gel content of less than 5 wt%. The resin acid is rosin.

2. The hydrophilic modified polypropylene fiber reinforced concrete material according to claim 1, characterized in that... Polypropylene and resin acid-modified polypropylene are melt-mixed, extruded through a spinneret of an extruder, cooled in a water bath at 10-30 degrees Celsius, and then the resulting fibers are drawn 6-10 times at 100-140 degrees Celsius. The fibers are then heat-set at 80-110 degrees Celsius, and finally cut to obtain the final product.

3. The hydrophilic modified polypropylene fiber reinforced concrete material according to claim 1, characterized in that... The irradiation source used was 60 Co cobalt source.

4. The hydrophilic modified polypropylene fiber reinforced concrete material according to claim 3, characterized in that... 60 The cobalt source was irradiated at a dose of 1-50 kGy.

5. The hydrophilic modified polypropylene fiber reinforced concrete material according to claim 4, characterized in that... 60 The preferred irradiation dose for the Co-cobalt source is 15~45 kGy.

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