A nano-modified glass steel pipe

Abstract

The present invention provides a nano-modified glass steel pipe, belonging to the technical field of glass steel pipes. It includes an inner layer, an outer layer and a sand-filled layer. The inner layer includes a lining layer, an inner circumferential winding layer and an inner axial fiber layer. The outer layer includes an outer axial fiber layer, an outer circumferential winding layer and an outer protective layer. The sand-filled layer is filled with a modified resin and quartz sand composite. The modified resin and quartz sand composite is prepared by adding hyperbranched modified silica to epoxy resin, stirring and mixing, then adding a crosslinking agent and a hindered urea curing agent, adding quartz sand, and heating and curing. The hyperbranched modified silica is prepared by reacting phytic acid and hyperbranched polyester on the surface of nano-silica with amino groups on the surface in sequence. The nano-modified glass steel pipe prepared by the present invention has a sand-filled layer filled with a modified resin and quartz sand composite, has high strength and toughness, stable thermal properties, good flame retardancy, and has self-healing properties, is not easy to be brittle or broken, and is easy to realize industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of fiberglass pipes, and particularly to a nano-modified fiberglass pipe. Background Art

[0002] At present, the sand-filled layer of a fiberglass sand-filled pipe is a resin mortar layer (a mixture of quartz sand and resin). The function of this layer is to transfer the forces between the inner and outer layers of the fiberglass pipe, improve the pipe stiffness, ensure a certain shear strength of the pipe, and avoid delamination during the flexural performance inspection of the product. The existing fiberglass sand-filled pipes usually use the method of directly mixing quartz sand and resin to obtain the sand-filled layer. Although the performance of the pipe is improved to a certain extent, in the case where high compressive strength and compressive toughness are required, the existing sand-filled pipes still cannot meet the requirements. Therefore, it is necessary to design a sand-filled pipe that can meet the requirements of high compressive strength and compressive toughness.

[0003] Chinese invention patent CN102705592B discloses a nano-modified fiberglass pipe, which sequentially includes an inner layer, a sand-filled layer, and an outer layer from inside to outside. The sand-filled layer is prepared by the following steps: (1) dispersively mixing nano-silica and / or nano-activated calcium carbonate with resin to obtain a modified resin matrix, wherein the weight ratio of nano-silica and / or nano-activated calcium carbonate is 1-8%; mixing the modified resin matrix with quartz sand, wherein the resin weight accounts for 15-18% of the total weight. However, the compatibility of the nano-silica and / or nano-activated calcium carbonate used in this patent in the resin is poor. Therefore, its performance is limited.

[0004] Chinese invention patent CN102691829B discloses a nano-modified fiberglass sand-filled pipe, which sequentially includes an inner layer, a sand-filled layer, and an outer layer from inside to outside. Through an independently designed nano-material mixing and dispersing process, 1-8% by weight of a two-component nano-material (a mixture of surface-treated nano-silica and nano-activated calcium carbonate) is uniformly mixed into the resin to obtain a mixed nano-material modified resin matrix, and then the resin matrix and quartz sand are fully mixed to form a sand-filled layer. Although surface-treated nano-materials are used in this patent, thus reducing the agglomeration of nano-materials to a certain extent, the mechanical enhancement effect still needs to be further improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a nano-modified fiberglass pipe. The sand-filled layer is filled with a modified resin and quartz sand composite prepared from self-healing epoxy resin and hyperbranched modified silica, which has high strength and toughness, stable thermal properties, good flame retardancy, and self-healing properties, is not easy to be brittle or broken, and is easy to realize industrial application.

[0006] The technical solution of the present invention is realized as follows:

[0007] The present invention provides a nano-modified glass steel pipe, which comprises an inner layer, an outer layer and a sand-filled layer. The sand-filled layer is filled with a modified resin and quartz sand composite. The modified resin and quartz sand composite is prepared by adding hyperbranched modified silica into epoxy resin, stirring and mixing, then adding a crosslinking agent and a hindered urea curing agent, adding quartz sand, and heating and curing. The mass ratio of the epoxy resin, hyperbranched modified silica, crosslinking agent, hindered urea curing agent and quartz sand is 100:7-12:2-4:15-20:20-40; the hyperbranched modified silica is prepared by reacting nano-silica with an amino group on the surface with phytic acid and hyperbranched polyester in sequence; the structure of the hindered urea curing agent is shown in Formula I:

[0008] Formula I;

[0009] The structural formula of the hyperbranched polyester is shown in Formula II:

[0010] Formula II.

[0011] As a further improvement of the present invention, the structural formula of the hyperbranched polyester is shown in Formula II:

[0012] Formula II;

[0013] The preparation method of the hyperbranched polyester is as follows: Pentaerythritol, trimellitic anhydride, a catalyst and a solvent are mixed and reacted, and heated until the acid value remains unchanged, and the solvent is removed under reduced pressure.

[0014] As a further improvement of the present invention, the molar ratio of pentaerythritol to trimellitic anhydride is 1:4, the addition amount of the catalyst is 0.1-0.15 wt% of the total mass of the reactants, the catalyst is p-toluenesulfonic acid or triphenylphosphine, the temperature of the heating reaction is 130-140 °C, and the solvent is DMF.

[0015] As a further improvement of the present invention, the preparation method of the hyperbranched modified silica is as follows:

[0016] S1. Preparation of silica with an amino group on the surface: An amino silane is dropped into water, stirred and reacted, centrifuged, washed, and spray-dried to obtain silica nano-spheres with an amino group on the surface;

[0017] S2. Phytic acid modification: The silica with an amino group on the surface is added into water, phytic acid and dipotassium hydrogen phosphate are added, and hydrothermal reaction is carried out, centrifuged, washed, and dried to obtain modified silica nano-spheres;

[0018] S3. Preparation of hyperbranched modified silica: Add hyperbranched polyester into DMF solvent, add NHS and EDC, stir for activation, add modified silica nanospheres, stir for reaction, centrifuge, wash, and dry to obtain hyperbranched modified silica.

[0019] Preferably, the aminosilane is selected from at least one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldiethoxysilane, and diethylenetriaminepropyltrimethoxysilane.

[0020] As a further improvement of the present invention, the rotation speed of the stirring reaction in step S1 is 1000 - 1500 r / min, the time is 6 - 10 h, and the reaction temperature is 50 - 60 °C; the mass ratio of the silica with amino groups on the surface, phytic acid, and dipotassium hydrogen phosphate in step S2 is 10 - 15:3 - 5:0.2 - 0.3, the temperature of the hydrothermal reaction is 130 - 140 °C, and the time is 5 - 7 h; the mass ratio of the hyperbranched polyester, modified silica nanospheres, NHS, and EDC in step S3 is 5 - 8:12 - 15:1 - 2:1 - 2, the time of the stirring activation is 20 - 30 min, and the time of the stirring reaction is 8 - 10 h.

[0021] As a further improvement of the present invention, the preparation method of the blocked urea curing agent is as follows: Under the protection of inert gas, dissolve diphenylmethane diisocyanate and triethylenediamine in a solvent, add N,N'-di-tert-butylethylenediamine, heat under reflux for reaction, and remove impurities and the solvent under reduced pressure to obtain the blocked urea curing agent.

[0022] As a further improvement of the present invention, the solvent is dichloromethane, the molar ratio of diphenylmethane diisocyanate to N,N'-di-tert-butylethylenediamine is 1:2, the addition amount of triethylenediamine is 0.2 - 0.5 wt% of the total mass of the reactants, and the time of the heating reflux reaction is 6 - 8 h.

[0023] As a further improvement of the present invention, the epoxy resin is E-51, and the crosslinking agent is 4,4'-diaminodiphenylmethane.

[0024] As a further improvement of the present invention, the conditions for heat curing are heating at 55 - 65 °C for 2 - 3 h, heating at 95 - 100 °C for 2 - 4 h, heating at 130 - 140 °C for 2 - 4 h, and heating at 150 - 160 °C for 0.5 - 1.5 h.

[0025] The present invention has the following beneficial effects:

[0026] The sand-filled layer of the nano-modified glass steel pipe of the present invention is filled with a modified resin and quartz sand composite. The modified resin and quartz sand composite is prepared by adding hyperbranched modified silica to epoxy resin, stirring and mixing, then adding a crosslinking agent and a hindered urea curing agent, adding quartz sand, and heating and curing. Among them, the epoxy resin is cured with a hindered urea curing agent. The stable conjugated system of the urea bond can be disrupted by adding bulky substituents to the nitrogen atom. Although this may hinder the strong interaction between the amine and the isocyanate, leading to the dissociation of the bond, however, because the isocyanate can easily react with the amine, new urea bonds can thus be quickly formed. Therefore, the bond is dynamically reversible. Therefore, the post-treatment behavior of the bulky hindered urea-based material at room temperature endows the material with an adaptable dynamic covalent network, so that the epoxy resin obtained by its curing crosslinking can achieve its self-healing performance under mild conditions, and also improves the toughness of the epoxy resin and reduces its brittleness, ensuring that the material has good mechanical properties.

[0027] In addition, hyperbranched modified silica is also added to the modified resin and quartz sand composite. First, amino silane is dropped into water. It is insoluble in water and is dispersed into tiny droplets during stirring. The amino group is protonated, stabilizing the silane droplets and providing an alkaline environment to catalyze the sol-gel reaction of the silane, thus obtaining silica nanospheres with amino groups on the surface. After the surface of the nanospheres further reacts with phytic acid, its amino group can then react with the polyester of the hyperbranched polyester, thus realizing the synchronous modification of phytic acid and hyperbranched polyester. On the one hand, phytic acid and hyperbranched modification improve the toughness of the resin, enhance the dispersion of nanoparticles in the epoxy resin material, and avoid the agglomeration of the nanomaterials themselves. At the same time, the remaining amino groups on the surface of the nanomaterials can also participate in the curing reaction of the epoxy resin, further improving the dispersion of the nanomaterials. Meanwhile, the introduction of the hyperbranched structure into the epoxy resin can form a good network structure with the epoxy resin. The inorganic nanoparticles act as the central nucleation points, significantly improving the impact strength of the epoxy resin, and also enhancing the tensile and flexural strengths, improving the thermal properties of the epoxy resin, and further enhancing its flame retardancy.

[0028] The sand-filled layer of the nano-modified glass steel pipe prepared by the present invention is filled with a modified resin and quartz sand composite, has high strength and toughness, stable thermal properties, good flame retardancy, and has self-healing performance, is not easy to be brittle or broken, and is easy to realize industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0030] Figure 1 It is a schematic structural diagram of the nano-modified glass steel pipe of the present invention;

[0031] Among them, 1 is the inner lining layer; 2 is the inner circumferential winding layer; 3 is the inner axial fiber layer; 4 is the sand-filled layer; 5 is the outer axial fiber layer; 6 is the outer circumferential winding layer; 7 is the outer protective layer.

[0032] Figure 2 It is a comparison chart of the self-healing experiments of the modified resin and quartz sand composite prepared in Example 3 at different temperatures. Specific Embodiments

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0034] NHS, N-hydroxysuccinimide; EDC, 1-ethyl-(3-dimethylaminopropyl)carbodiimide; particle size range of quartz sand: 10-20 mesh, 40 wt%, 30-60 mesh, 20 wt%, 70-100 mesh, 25 wt%, >100 mesh, 15 wt%.

[0035] Preparation Example 1 Preparation of Hyperbranched Polyester

[0036] Synthesis route:

[0037] ;

[0038] The method is as follows:

[0039] Mix 10 mmol of pentaerythritol, 40 mmol of trimellitic anhydride, triphenylphosphine and 50 mL of DMF solvent for reaction. The addition amount of the catalyst is 0.12 wt% of the total mass of the reactants. Heat to 135 °C and stir the reaction until the acid value remains unchanged. Remove the solvent under reduced pressure. ESI-MS calculated value: C 41 H 29 O 24 (M+H) + 905.10, measured value: 905.1, yield is 95%.

[0040] NMR result: 1 H NMR (300 MHz, CDCl3) δ 11.2 (br, 8H), 9.12 (s, 4H), 8.62 (d, J J = 6.4 Hz, 4H), 8.37 (d, J J = 6.3 Hz, 4H), 4.22 (s, 8H).

[0041] Preparation Example 2 Preparation of the blocked urea curing agent

[0042] Synthesis route:

[0043] ;

[0044] The method is as follows: Under nitrogen protection, 10 mmol of diphenylmethane diisocyanate and triethylenediamine are dissolved in 50 mL of dichloromethane. The addition amount of triethylenediamine is 0.3 wt% of the total mass of the reactants. 20 mmol of N,N'-di-tert-butylethylenediamine is added, and the mixture is heated under reflux for 8 h. Impurities and solvents are removed under reduced pressure to obtain the blocked urea curing agent. ESI-MS calculated value: C 35 H 59 N6O2 (M+H) + 595.46, measured value: 595.5, and the yield is 87%.

[0045] NMR result: 1 H NMR (300 MHz, CDCl3) δ 7.65 (d, J J = 6.1 Hz, 4H), 7.12 (d, J J = 6.2 Hz, 4H), 6.0 (br, 2H), 3.82 (s, 2H), 3.32 (t, 4H), 2.93 (t, 4H), 3.0 (br, 2H), 1.42 (s, 18H), 1.22 (s, 18H).

[0046] Preparation Example 3 Preparation of hyperbranched modified silica

[0047] The method is as follows:

[0048] S1. Preparation of silica with amino groups on the surface: 2 g of N-β(aminoethyl)-γ-aminopropyltrimethoxysilane is dropped into 200 mL of water, and the mixture is stirred at 1000 r / min and 50 °C for 6 h, centrifuged, washed, and spray-dried to obtain silica nanospheres with amino groups on the surface;

[0049] S2. Phytic acid modification: Add 10 g of silica with amino groups on the surface to 200 mL of water, add 3 g of phytic acid and 0.2 g of dipotassium hydrogen phosphate, carry out hydrothermal reaction at 130 °C for 5 h, centrifuge, wash, and dry to obtain modified silica nanospheres;

[0050] S3. Preparation of hyperbranched modified silica: Add 5 g of the hyperbranched polyester prepared in Preparation Example 1 to 200 mL of DMF solvent, add 1 g of NHS and 1 g of EDC, stir and activate for 20 min, add 12 g of modified silica nanospheres, stir and react for 8 h, centrifuge, wash, and dry to obtain hyperbranched modified silica.

[0051] Preparation Example 4 Preparation of hyperbranched modified silica

[0052] The method is as follows:

[0053] S1. Preparation of silica with amino groups on the surface: Drop 2 g of γ-aminopropyltriethoxysilane into 200 mL of water, stir and react at 1500 r / min and 60 °C for 10 h, centrifuge, wash, and spray dry to obtain silica nanospheres with amino groups on the surface;

[0054] S2. Phytic acid modification: Add 12 g of silica with amino groups on the surface to 200 mL of water, add 5 g of phytic acid and 0.3 g of dipotassium hydrogen phosphate, carry out hydrothermal reaction at 140 °C for 7 h, centrifuge, wash, and dry to obtain modified silica nanospheres;

[0055] S3. Preparation of hyperbranched modified silica: Add 8 g of the hyperbranched polyester prepared in Preparation Example 1 to 200 mL of DMF solvent, add 2 g of NHS and 2 g of EDC, stir and activate for 30 min, add 15 g of modified silica nanospheres, stir and react for 10 h, centrifuge, wash, and dry to obtain hyperbranched modified silica.

[0056] Preparation Example 5 Preparation of hyperbranched modified silica

[0057] The method is as follows:

[0058] S1. Preparation of silica with amino groups on the surface: Drop 2 g of γ-aminopropyltrimethoxysilane into 200 mL of water, stir and react at 1200 r / min and 55 °C for 8 h, centrifuge, wash, and spray dry to obtain silica nanospheres with amino groups on the surface;

[0059] S2. Phytic acid modification: Add 12 g of silica with amino groups on the surface to 200 mL of water, add 4 g of phytic acid and 0.25 g of dipotassium hydrogen phosphate, carry out hydrothermal reaction at 135 °C for 6 h, centrifuge, wash, and dry to obtain modified silica nanospheres;

[0060] S3. Preparation of hyperbranched modified silica: Add 6.5 g of the hyperbranched polyester prepared in Preparation Example 1 to 200 mL of DMF solvent, add 1.5 g of NHS and 1.5 g of EDC, stir and activate for 25 min, add 13.5 g of modified silica nanospheres, stir and react for 9 h, centrifuge, wash, and dry to obtain hyperbranched modified silica.

[0061] Comparative Preparation Example 1

[0062] Compared with Preparation Example 5, the difference lies in that step S2 is not carried out.

[0063] Specifically as follows:

[0064] S1. Preparation of silica with amino groups on the surface: Drop 2 g of γ-aminopropyltrimethoxysilane into 200 mL of water, stir and react at 1200 r / min and 55 °C for 8 h, centrifuge, wash, and spray dry to obtain silica nanospheres with amino groups on the surface;

[0065] S2. Preparation of hyperbranched modified silica: Add 6.5 g of the hyperbranched polyester prepared in Preparation Example 1 to 200 mL of DMF solvent, add 1.5 g of NHS and 1.5 g of EDC, stir and activate for 25 min, add 13.5 g of silica nanospheres with amino groups on the surface, stir and react for 9 h, centrifuge, wash, and dry to obtain hyperbranched modified silica.

[0066] Comparative Preparation Example 2

[0067] Compared with Preparation Example 5, the difference lies in that step S3 is not carried out.

[0068] Specifically as follows:

[0069] S1. Preparation of silica with amino groups on the surface: Drop 2 g of γ-aminopropyltrimethoxysilane into 200 mL of water, stir and react at 1200 r / min and 55 °C for 8 h, centrifuge, wash, and spray dry to obtain silica nanospheres with amino groups on the surface;

[0070] S2. Phytic acid modification: Add 12 g of silica with amino groups on the surface to 200 mL of water, add 4 g of phytic acid and 0.25 g of dipotassium hydrogen phosphate, carry out hydrothermal reaction at 135 °C for 6 h, centrifuge, wash, and dry to obtain modified silica nanospheres.

[0071] Comparative Preparation Example 3

[0072] Compared with Preparation Example 5, the difference lies in that steps S2 and S3 are not carried out.

[0073] Preparation of silica with amino groups on the surface: 2 g of γ-aminopropyltrimethoxysilane was dropped into 200 mL of water, and stirred at 1200 r / min and 55 °C for 8 h, then centrifuged, washed, and spray-dried to obtain silica nanospheres with amino groups on the surface.

[0074] Example 1: As Figure 1 , the nano-modified glass steel pipe of the present invention comprises an inner layer, an outer layer and a sand-filled layer. Among them, the inner layer includes a lining layer 1, an inner circumferential winding layer 2, and an inner axial fiber layer 3. The outer layer includes an outer axial fiber layer 5, an outer circumferential winding layer 6, and an outer protective layer 7. The sand-filled layer 4 is filled with a modified resin and quartz sand composite. Among them, the preparation method of the modified resin and quartz sand composite is as follows:

[0075] 7 g of the hyperbranched modified silica prepared in Preparation Example 3 was added to 100 g of epoxy resin E-51, stirred and mixed for 20 min, 2 g of 4,4'-diaminodiphenylmethane and 15 g of the blocked urea curing agent prepared in Preparation Example 2 were added, 20 g of quartz sand was added, and heated and cured to obtain a modified resin and quartz sand composite;

[0076] The conditions for heating and curing were heating at 55 °C for 2 h, heating at 95 °C for 2 h, heating at 130 °C for 2 h, and heating at 150 °C for 0.5 h.

[0077] Example 2: As Figure 1 , the nano-modified glass steel pipe of the present invention comprises an inner layer, an outer layer and a sand-filled layer. Among them, the inner layer includes a lining layer 1, an inner circumferential winding layer 2, and an inner axial fiber layer 3. The outer layer includes an outer axial fiber layer 5, an outer circumferential winding layer 6, and an outer protective layer 7. The sand-filled layer 4 is filled with a modified resin and quartz sand composite. Among them, the preparation method of the modified resin and quartz sand composite is as follows:

[0078] 12 g of the hyperbranched modified silica prepared in Preparation Example 4 was added to 100 g of epoxy resin E-51, stirred and mixed for 20 min, 4 g of 4,4'-diaminodiphenylmethane and 20 g of the blocked urea curing agent prepared in Preparation Example 2 were added, 40 g of quartz sand was added, and heated and cured to obtain a modified resin and quartz sand composite;

[0079] The conditions for heating and curing were heating at 65 °C for 3 h, heating at 100 °C for 4 h, heating at 140 °C for 4 h, and heating at 160 °C for 1.5 h.

[0080] Example 3: As Figure 1, the nano-modified glass steel pipe of the present invention comprises an inner layer, an outer layer and a sand-filled layer. Among them, the inner layer includes a lining layer 1, an inner circumferential winding layer 2 and an inner axial fiber layer 3, the outer layer includes an outer axial fiber layer 5, an outer circumferential winding layer 6 and an outer protective layer 7, and the sand-filled layer 4 is filled with a modified resin and quartz sand composite. Among them, the preparation method of the modified resin and quartz sand composite is as follows:

[0081] Add 10 g of hyperbranched modified silica prepared in Preparation Example 5 to 100 g of epoxy resin E-51, stir and mix for 20 min, add 3 g of 4,4'-diaminodiphenylmethane and 17 g of the blocked urea curing agent prepared in Preparation Example 2, add 30 g of quartz sand, and heat and cure to obtain a modified resin and quartz sand composite;

[0082] The conditions for heat curing are heating at 60 °C for 2.5 h, heating at 98 °C for 3 h, heating at 135 °C for 3 h, and heating at 155 °C for 1 h.

[0083] Self-healing performance test: Scratch the surface of the sample with a knife, the scratch width is about 25 μm, keep it warm at 100, 110, and 120 °C for 10 min in turn, and observe the morphology of the damaged coating during the self-healing process through an optical microscope. The results are shown in Figure 2 , as can be seen from the figure, the scratches on the sample prepared by the present invention are hardly visible after heating at 110 °C or above for 10 min, indicating good self-healing ability.

[0084] Comparative Example 1

[0085] Compared with Example 3, the difference is that the hyperbranched modified silica is replaced by the product prepared in Comparative Preparation Example 1.

[0086] Comparative Example 2

[0087] Compared with Example 3, the difference is that the hyperbranched modified silica is replaced by the product prepared in Comparative Preparation Example 2.

[0088] Comparative Example 3

[0089] Compared with Example 3, the difference is that the hyperbranched modified silica is replaced by the product prepared in Comparative Preparation Example 3.

[0090] Comparative Example 4

[0091] Compared with Example 3, the difference is that no hyperbranched modified silica is added.

[0092] Test Example 1

[0093] Perform mechanical property tests on the modified resin and quartz sand composites prepared in Examples 1-3 and Comparative Examples 1-4. The results are shown in Table 1.

[0094] The tensile property test was carried out with reference to GB / T 2567-2021, measured at 25 °C, and the test speed was 10 mm / min.

[0095] The impact property test was carried out with reference to GB / T 2567-2021. The non-notch impact method was selected, and a plastic pendulum impact testing machine was used for the test. The specimen size was 120 mm×15 mm×10 mm.

[0096] The tensile shear strength test was carried out with reference to GB / T7124-2008. A 100 mm×25 mm×1.6 mm SUS 321 stainless steel sheet was selected. The length of the bonding surface was 12.5±0.25 mm, the width was 25±0.25 mm, the thickness of the adhesive layer was about 0.2 mm. The overflow glue was cleaned up in time. After curing for 2 days, the test was carried out at 25 °C using a universal tensile testing machine with a test speed of 2 mm / min.

[0097] Table 1

[0098] As can be seen from the above table, the modified resin and quartz sand composites prepared in Examples 1-3 of the present invention have good mechanical properties.

[0099] Test Example 2

[0100] The flame retardancy performance tests of the modified resin and quartz sand composites prepared in Examples 1-3 and Comparative Examples 1-4 were carried out with reference to the standard GB / T 2406.2-2009. The results are shown in Table 2.

[0101] Table 2 ;

[0102] As can be seen from the above table, the modified resin and quartz sand composites prepared in Examples 1-3 of the present invention have good flame retardancy performance.

[0103] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A nano-modified glass steel pipe, which comprises an inner layer, an outer layer and a sand-filled layer. The inner layer includes a lining layer, an inner circumferential winding layer and an inner axial fiber layer. The outer layer includes an outer axial fiber layer, an outer circumferential winding layer and an outer protective layer, and is characterized in that The sand-interlayer is filled with a modified resin and quartz sand composite, wherein the modified resin and quartz sand composite is prepared by adding hyperbranched modified silica to epoxy resin, stirring and mixing, adding a crosslinking agent and a hindered urea curing agent, adding quartz sand, and heating and curing, wherein the mass ratio of the epoxy resin, the hyperbranched modified silica, the crosslinking agent, the hindered urea curing agent and the quartz sand is 100:7-12:2-4:15-20:20-40; The structure of the hindered urea curing agent is shown in Formula I: Formula I; The preparation method of the hyperbranched modified silica is as follows: S1. Preparation of silica with amino groups on the surface: dropping aminosilane into water, stirring the reaction, centrifuging, washing, and spray drying to obtain silica nanospheres with amino groups on the surface; S2. Phytic acid modification: adding silica with amino groups on the surface to water, adding phytic acid and dipotassium hydrogen phosphate, hydrothermally reacting, centrifuging, washing, and drying to obtain modified silica nanospheres; the mass ratio of the silica with amino groups on the surface, phytic acid, and dipotassium hydrogen phosphate is 10-15:3-5:0.2-0.3; S3. Preparation of hyperbranched modified silica: adding a hyperbranched polyester to an N,N-dimethylformamide solvent, adding N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide, stirring for activation, adding modified silica nanospheres, stirring for reaction, centrifuging, washing, and drying to obtain hyperbranched modified silica; the mass ratio of the hyperbranched polyester, modified silica nanospheres, N-hydroxysuccinimide and 1-ethyl-(3-dimethylaminopropyl)carbodiimide is 5-8:12-15:1-2:1-2; The structural formula of the hyperbranched polyester is shown in Formula II: Formula II.

2. The nano-modified glass steel pipe according to claim 1, wherein The preparation method of the hyperbranched polyester is as follows: pentaerythritol, trimellitic anhydride, a catalyst and a solvent are mixed for reaction, heated for reaction until the acid value remains unchanged, and the solvent is removed under reduced pressure.

3. The nano-modified glass steel pipe according to claim 2, characterized in that, The molar ratio of pentaerythritol to trimellitic anhydride is 1:4, the added amount of the catalyst is 0.1-0.15wt% of the total mass of the reactants, the catalyst is p-toluenesulfonic acid or triphenylphosphine, the temperature of the heating reaction is 130-140°C, and the solvent is ‌N,N-dimethylformamide.

4. The nano-modified glass steel pipe according to claim 1, characterized in that, The speed of the stirring reaction in step S1 is 1000-1500r / min, the time is 6-10h, and the reaction temperature is 50-60°C; the temperature of the hydrothermal reaction in step S2 is 130-140°C, and the time is 5-7h; the time of the stirring activation in step S3 is 20-30min, and the stirring reaction time is 8-10h.

5. The nano-modified glass steel pipe according to claim 1, characterized in that, The preparation method of the hindered urea curing agent is as follows: under the protection of inert gas, diphenylmethane diisocyanate and triethylenediamine are dissolved in a solvent, N,N'-di-tert-butylethylenediamine is added, heated under reflux reaction, and impurities and solvent are removed under reduced pressure to obtain the hindered urea curing agent.

6. The nano-modified glass steel pipe according to claim 5, characterized in that, The solvent is dichloromethane, the molar ratio of diphenylmethane diisocyanate to N,N'-di-tert-butylethylenediamine is 1:2, the addition amount of triethylenediamine is 0.2-0.5 wt% of the total mass of the reactants, and the time for the heating reflux reaction is 6-8 h.

7. The nano-modified glass steel pipe according to claim 1, characterized in that, The epoxy resin is E-51 and the crosslinking agent is 4,4'-diaminodiphenylmethane.

8. The nano-modified glass steel pipe according to claim 1, wherein The conditions for the heat curing are heating at a temperature of 55-65°C for 2-3 h, heating at a temperature of 95-100°C for 2-4 h, heating at a temperature of 130-140°C for 2-4 h, and heating at a temperature of 150-160°C for 0.5-1.5 h.

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