Modified reactive resin compositions and use thereof for coating propping agents

Abstract

Proppants coated with a cured reactive resin composition containing 92-99.5 wt. % of a reactive resin and 0.5 to 8 wt. % of a silicone resin containing at least 5 wt. % of alkoxy groups and at least 20 mol percent of T and/or Q units, in liquid form, exhibit high freedom from fines generation, and are free flowing.

Claims

1. A reactive resin composition, comprising: a physical admixture of (A) 92%-99.5% by weight of at least one reactive phenol/formaldehyde resin, and (B) 0.5%-8% by weight of at least one silicone resin comprising units of the formulae (Ia), (Ib), (VII) and (Id) ##STR00003## where R.sup.17 each is an identical or different monovalent, optionally substituted organic radical optionally bearing functional groups, OH, or a hydrogen radical, with the provisos that in (B) at least 20 mol % of the formula (Ia) or (Ib) or a mixture thereof is present, in (B) at most 50 mol % of the formula (Ib) is present, alkoxy groups are present in (B) as R.sup.17 to an extent of at least 5% by weight, prepared by the process of dissolving and/or dispersing (B) into (A), and isolating a product comprising reactive resin (A) which has not reacted with (B).

2. The reactive resin composition of claim 1, wherein (B) comprises at least 8.5% by weight of alkoxy groups.

3. The reactive resin composition of claim 1, wherein at least 10 mol % of all R.sup.17 radicals are independently identical or different monovalent optionally substituted organic radicals having at least 3 carbon atoms.

4. The reactive resin composition of claim 3, wherein as further R.sup.17 radicals, at least 1 mol % are independently selected from organofunctional radicals and silicon-bonded hydrogen.

5. The reactive resin composition of claim 1, wherein at least 1 mol % of all R.sup.17 radicals are independently organofunctional radicals or silicon-bonded hydrogen.

6. A process for preparing the reactive resin composition of claim 1, comprising: dispersing (B) in (A) with the proviso that (A) is free-flowing at 20 C., (A) has been rendered free-flowing by prior heating up to 250 C. or (A) has been dissolved in a suitable solvent to render it free-flowing.

7. A solid coating, molding, workpiece, or foam, comprising a cured reactive resin composition of claim 1.

8. A proppant having a cured coating of a reactive resin composition of claim 1.

9. A process for producing coated proppants, comprising: providing a coating composition comprising a reactive resin composition of claim 1 in free-flowing form, optionally adding one or more hardener(s) (C) to the reactive resin composition, and optionally adding one or more additive(s) (D) to the reactive resin composition, coating proppant particles with the coating composition, and then curing the reactive resin composition.

10. A coated proppant prepared by the process of claim 9.

11. A process for producing coated proppants, comprising: i) producing a reactive resin composition of claim 1 as an in situ process in the presence of the proppant, by mixing at least one (B) and at least one (A) which is free-flowing at 20 C., or with (A) that has been rendered free-flowing by prior heating to up to 250 C., or with (A) which has been dissolved in a suitable solvent, and proppant particles, optionally adding one or more hardener(s) (C) optionally adding one or more additive(s) (D), ii) and thereafter curing the reactive resin composition to form coated proppant particles.

12. A coated proppant prepared by the process of claim 11.

13. In a fracking production method for mineral oil and natural gas production wherein a proppant is employed, the improvement comprising employing a proppant coated with a cured reactive resin composition of claim 1.

14. A reactive resin composition suitable for use in coating proppant particles, consisting of: 1) a physical admixture of A) a phenol/formaldehyde reactive resin in an amount of from 92 to 99.5 weight percent, and B) from 0.5 to 8 weight percent of a silicone resin containing units of the formulae (Ia), (Ib), (VII), and (Id) ##STR00004## where R.sup.17 each is an identical or different monovalent, optionally substituted organic radical optionally bearing functional groups, OH, or a hydrogen radical, with the provisos that in (B) at least 20 mol % of the formula (Ia) or (Ib) or a mixture thereof is present, in (B) at most 50 mol % of the formula (Ib) is present, alkoxy groups are present in (B) as R.sup.17 to an extent of at least 5% by weight, and wherein the silicone resin (B) is dispersed in, dissolved in, or both dissolved and dispersed in unmodified reactive resin (A); 2) optionally, one or more hardeners for the unmodified reactive resin (A); and 3) optionally, one or more additives selected from the group consisting of antistats, separating agent, and adhesion promoters.

15. The reactive resin composition of claim 14, wherein urotropin is present as a hardener.

16. A process for producing coated proppant particles, comprising coating proppant particles with an uncured coating composition of claim 14, and curing the coating composition to produce coated proppant particles.

Description

EXAMPLES

(1) The examples which follow elucidate the invention without having any limiting effect. In the examples described hereinafter, all figures given for parts and percentages, unless stated otherwise, are based on weight. Unless stated otherwise, the examples which follow are conducted at a pressure of the surrounding atmosphere, i.e. at about 1000 hPa, and at room temperature, i.e. at 25 C., or at a temperature which is established on combination of the reactants at room temperature without additional heating or cooling. All viscosity figures hereinafter relate to a temperature of 25 C.

(2) Abbreviations Used:

(3) The meaning of the abbreviations used further up also applies to the examples:

(4) PTFE=polytetrafluoroethylene

(5) rpm=revolutions per minute

(6) Molecular Weight Distributions:

(7) Molecular weight distributions are determined as the weight average Mw and as the number average Mn, employing the method of gel permeation chromatography (GPC or size exclusion chromatography (SEC)) with polystyrene standard and refractive index detector (RI detector). Unless stipulated otherwise, THF is used as eluent and DIN 55672-1 is employed. The polydispersity is the quotient Mw/Mn.

Example 1

(8) A glass flask was purged with nitrogen, charged with 475 g of novolak Resin 14772 (Plastics Engineering Company, Sheboygan, USA) and purged with nitrogen once again. The material was melted at 120 C. Then a stirrer was switched on at 420 rpm. 25 g of silicone resin 1 of the composition [PhSiO.sub.3/2].sub.7.3.5 [(3-glycidoxypropyl)SiO.sub.3/2].sub.4.20 [Me.sub.2SiO.sub.2/2].sub.3.45 [MeO.sub.1/2].sub.6.68 [BuO.sub.1/2].sub.0.64 (molecular weight according to SEC (THF eluent): Mw=2100 g/mol; Mn=1300 g/mol; viscosity 90-135 cSt; epoxy equivalent weight 660-680 g/mol; epoxy value 1.85 mmol/g) were added and the mixture was stirred at 420 rpm, 10 minutes. The liquid material is poured hot onto a PTFE film and mechanically comminuted, and hence a granular material is produced.

Example 2

(9) By the process of example 1, 25 g of silicone resin 2 of the composition [PhSiO.sub.3/2].sub.7.30 [(2-amino-ethyl)-3-aminopropyl-SiO.sub.3/2].sub.2.62 [Me.sub.2SiO.sub.2/2].sub.3.86 [MeO.sub.1/2].sub.5.88 [BuO.sub.1/2].sub.0.57 (molecular weight according to SEC (THF/acetic anhydride eluent): Mw=1800 g/mol; Mn=1200 g/mol; viscosity (kinematic, 25 C.) 120 mm.sup.2/s; amine value 2.6-2.9 mmol/g) rather than silicone resin 1 were incorporated and a granular material was produced.

Example 3

(10) By the process of example 1, 25 g of silicone resin 3 of the composition [PhSiO.sub.3/2].sub.9.44 [MeSiO.sub.3/2].sub.5.67 [Me.sub.2SiO.sub.2/2].sub.0.63 [MeO.sub.1/2].sub.6.77 (molecular weight according to SEC (THF eluent): Mw=1800 g/mol; Mn=900 g/mol; viscosity (kinematic, 25 C.) 280 mm.sup.2/s) rather than silicone resin 1 were incorporated and a granular material was produced.

Example 4

(11) By the process of example 1, 25 g of silicone resin 4 of the composition [MeSiO.sub.3/2].sub.23.14 [EtO.sub.1/2].sub.27.28 (molecular weight according to SEC (toluene eluent): Mw=2560 g/mol; Mn=900 g/mol; viscosity (dynamic, 25 C.) 25 mPa.Math.s) rather than silicone resin 1 were incorporated and a granular material was produced.

Comparative Example 1 (V1)

(12) By the process of example 1, 25 g of silicone resin 5 of the composition [Me.sub.3SiO.sub.1/2].sub.26.65 [ViMe.sub.2SiO.sub.1/2].sub.3.72 [SiO.sub.4/2].sub.42.78 [HO.sub.1/2].sub.1.02 [EtO.sub.1/2].sub.5.93 (molecular weight according to SEC (toluene eluent): Mw=5300 g/mol; Mn=2560 g/mol) rather than silicone resin 1 were incorporated and a granular material was produced.

Comparative Example 2 (V2)

(13) A glass flask was purged with nitrogen, charged with 475 g of novolak Resin 14772 (Plastics Engineering Company, Sheboygan, USA) and purged once again with nitrogen. The material was melted at 120 C. Then a stirrer was switched on at 420 rpm. 25 g of silicone resin 3 of the composition [PhSiO.sub.3/2].sub.9.44 [MeSiO.sub.3/2].sub.5.67 [Me.sub.2SiO.sub.2/2].sub.0.63 [MeO.sub.1/2].sub.6.77 (molecular weight according to SEC (THF eluent): Mw=1800 g/mol; Mn=900 g/mol; viscosity (kinematic, 25 C.) 280 mm.sup.2/s) and 5 g of oxalic acid were added and the mixture was stirred at 420 rpm initially at 130 C. under reflux for 1 h. Then the mixture was heated to 180 C. within 2 h and condensate that occurred was removed. This was followed by distillation at 180 C. for a further 30 min. The fluid mass was poured hot onto a PTFE film and mechanically comminuted and hence a granular material was produced.

(14) No catalyst was added in the mixing of the silicone resin (B) and the reactive resin (A) in inventive examples 1-4 and in noninventive comparative example V1. A physical mixture is formed. In noninventive comparative example V2, a catalyst was added and reacted at elevated temperature for a prolonged period. A hybrid material is the result of chemical reaction of novolak and silicone resin. In comparative example V2, a silicone resin containing D groups of the formula [Me.sub.2SiO.sub.2/2] was used, as disclosed in US20140124200A.

(15) It was found that, unexpectedly, the silicone resins (B) of the invention are distributed uniformly and finely in the reactive resin. If a second phase is formed, it is essentially in the form of spherical droplets. By contrast the solid noninventive polysiloxane from comparative example V1 is not finely dispersible and forms uneven lumps and fragments in the phenolic resin, some of which are up to 100 m in size.

Comparative Example 3 (V3)

(16) Comparative example V3 was unmodified novolak Resin 14772 (Plastics Engineering Company, Sheboygan, USA).

Example 6

(17) Preparation of Reactive Resin Solutions for Production of Test Specimens and Coating of Q-PANEL Test Sheets:

(18) 10 parts in each case of the inventive modified phenol resins from example 3 or 10 parts of the noninventive modified phenol resin from comparative example V2 or 10 parts of the pure modified phenol Resin 14772 (Plastics Engineering Company, Sheboygan, USA) were dissolved in each case together with 1 part urotropin and 10.0 parts ethyl acetate (from Bernd Kraft, >=99%) by agitation overnight.

Example 7

(19) Production of Phenolic Resin-Coated Q-PANEL Test Sheets:

(20) For the brittleness determination experiments, Q-PANEL test sheets were cleaned 3 with acetone on the brushed side and then flashed off in a fume hood for 1 h. Subsequently, 3 mL of the appropriate phenolic resin solution from example 6 were applied to each sheet and spread with a 100 m coating bar, and then the solution was evaporated off in a fume hood overnight.

(21) For hardening, the samples were placed into a cold drying cabinet, heated up to 160 C. while purging with nitrogen within 3 hours, kept at this temperature for 2 h and cooled down to 23 C. overnight.

(22) The evaporation of the solvent gives rise to an about 50 m-thick hardened resin layer on the sheet.

Example 8

(23) Testing of Durability:

(24) By means of a ball impact tester, it is possible to examine the stability of the coating in isolated form. A conclusion is obtained with regard to the elasticity, impact resistance and fracture resistance of a coating.

(25) For detection of the improved properties, i.e. toughness and impact resistance to impacts and pressure, according to Examples 6 and 7, a hardened layer of the inventive resins from example 3 of thickness about 50 m in each case was produced on a Q-PANEL test sheet, or, as comparative examples, a hardened layer of the unmodified Resin 14772 (Plastics Engineering Company, Sheboygan, USA) of thickness about 50 m and of the noninventive resin from comparative example V2. The coated sheets were tested in an Erichsen ball impact tester, model 304-ASTM, and the results were visually evaluated by a trained tester: for this purpose, a ball was allowed to fall from a defined, variable drop height onto the reverse side of the sheet (twin experiments in each case at different sites). The impact energy is found from the drop height multiplied by drop weight, reported in inches (in)pounds (lbs). The impact energy is altered as follows: 5, 10, 15, 20, 25, 30, 35, 40 (inlbs). The bulging impact sites were assessed visually for fissures and cracks and assessed relative to the reference.

(26) Table 1 shows the assessment of the resin coating on Q-PANEL test sheets and the stability thereof by means of a ball impact tester.

(27) TABLE-US-00001 TABLE 1 Resin from Siloxane Impact example additive test Description 3 Silicone ++ cracking from resin 3 35 inch lbs; flaking from 40 in lbs V2 Silicone + cracking from resin 3 10 inch lbs; flaking from 25 in lbs V3 No additive 0 cracking from 5 inch lbs

(28) The values should be understood as follows:

(29) 0 means a cracking profile similar to the reference. The reference shows distinct cracking even at the lowest energy, from 5 inchlbs. The extent of cracking is similar to the reference.

(30) + means a better cracking profile than the reference, meaning that distinct cracks are only apparent at a higher energy in the range of 10-30 inchlbs, or the extent of cracking is distinctly reduced overall compared to the reference. ++ means that no cracks are apparent up to an energy of 30 inchlbs.

(31) Completely surprisingly, the cured coating of the invention in Example 3 has significantly improved elasticity, impact resistance and fracture resistance compared to the unmodified comparative example V3 and to the laboriously producible hybrid material from noninventive comparative example V2, which contains the same silicone resin.

Example 9

(32) Production of Coated Proppants:

(33) 20-40 mesh fracking sand were coated with 3.5% of the inventive resins from examples 1 and 2, or, as comparative examples, with 3.5% of the unmodified Resin 14772 (Plastics Engineering Company, Sheboygan, USA) and of the noninventive resin from comparative example V1 by a melting method and cured with 10% by weight of urotropin, based on the amount of resin.

Example 10

(34) Study of Pressure Stability of Coated Proppants:

(35) The pressure stability of the coated proppants according to example 8 was studied according to DIN EN ISO 13503-2 at pressure 14000 PSI and 18000 PSI. The result is shown in table 2.

(36) TABLE-US-00002 TABLE 2 Amount of fines formed relative to the proppants having unmodified coating with resin Fracking sand coated with from Comparative Example V3 (%) resin from example at 14,000 PSI at 18,000 PSI 1 82 87 2 82 81 V1 98 104 V3 100 100

(37) It is found that, completely surprisingly, about 15-20% less fines is formed in the case of the proppants coated in accordance with the invention compared to the proppants with unmodified coating and to non-inventively coated resin from Comparative Example V1. The improvement in the compressive strength of the proppants coated in accordance with the invention was entirely unexpected, since an improvement in the fracture and impact resistance of the reactive resins modified in accordance with the invention did not permit any fundamental conclusion that this will automatically also lead to an improvement in compressive strength.