Unsaturated carbon-containing thermosetting resin and method for preparing the same

Abstract

To provide an unsaturated carbon-containing thermosetting resin, and a method for preparing the same.SOLUTION: An unsaturated carbon-containing thermosetting resin has a structure represented by formula (1), in which each symbol in formula (1) is defined in the specification. The unsaturated carbon-containing thermosetting resin is prepared from a polyphenylene ether compound and a maleimide compound having high rigidity and high thermal stability, and is reactive with a crosslinking agent. Thereby, the unsaturated carbon-containing thermosetting resin is applied to a packaging process of a printed circuit board, and a printed circuit board material excellent in heat resistance can be obtained.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to resins and methods for preparing the same, and more particularly to unsaturated carbon-containing thermosetting resins and methods for preparing the same that can improve the physical properties of the resins. [Background technology]

[0002] Recent trends in the development of electronic products include miniaturization, weight reduction, integration of components, and increased speed. Currently, the industrial technology of printed circuit boards (PCBs), both rigid and flexible, is evolving in the direction of high frequency, high speed, and high-density mounting, resulting in increasingly stringent material requirements. Furthermore, because mobile data transmission requires the transfer of large amounts of data, the related processes and materials are often developed in the high-frequency band (above 1 GHz). Key material properties include low dielectric constant (κ dielectric; Dk), low dielectric loss (dissipation factor; Df), high heat resistance, and good mechanical strength. Thermosetting resins possess chemical resistance, material rigidity, thermal stability, insulation, and low dielectric loss, and thus meet the application requirements for printed circuit board materials, making them widely used materials in printed circuit boards.

[0003] However, conventional thermosetting resins have poor adhesion to substrates, and their thermal stability and mechanical strength also need improvement. Furthermore, in the actual production process, conventional thermosetting resins have unstable weight molecular weight between production lots, which affects the stability of the packaging process later used for printed circuit boards.

[0004] In light of this, there is a need to develop a thermosetting resin having a good rigid structure, high thermal stability, and a stable weight-molecular-weight distribution. This thermosetting resin can be used as a substrate for printed circuit boards, contributing to obtaining a printed circuit board substrate with good mechanical strength and being advantageous in improving the stability of the packaging process for printed circuit boards. [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide an unsaturated carbon-containing thermosetting resin having good mechanical properties and thermal stability, and a method for preparing the same. The polymer chain segments of this unsaturated carbon-containing thermosetting resin have a rigid structure, which can improve the mechanical strength and thermal stability of the material, and have a high glass transition temperature (Tg). When this unsaturated carbon-containing thermosetting resin is used in printed circuit boards, the thermally stable unsaturated carbon-containing thermosetting resin contributes to the production stability of the printed circuit board process under the high-temperature environment of the lamination process and soldering process of the printed circuit board. Furthermore, because the molecular structure of the unsaturated carbon-containing thermosetting resin is symmetrical, the dielectric loss coefficient (Df) of the material is low, which meets the material requirements for high-frequency printed circuit boards, resulting in low signal loss under high-frequency transmission of the printed circuit board. [Means for solving the problem]

[0006] According to one aspect of the present invention, the structure is as shown in formula (1) below, [ka] X is -CH2-, -CH(CH3)-, or -C(CH3)2-, R1, R2, R3, R4, R5, R6, R7, and R8 are each independently a hydrogen atom or a C1-C3 hydrocarbon, a and b are each independently a numerical value between 2 and 500, Y is the structure shown in formula (2), and c and d are each independently a numerical value between 1 and 300. [ka] R9 is C4-C 20 It is a hydrocarbon, where E is the structure shown in formula (3), F is the structure shown in formula (4), and e and f are each independent numerical values ​​from 1 to 200. [ka] R 10 These are C2-C6 straight-chain or branched-chain hydrocarbons,

Chem.

Chem.

[0007] According to the unsaturated carbon-containing thermosetting resin described in the previous paragraph, Y may have the structure shown in formula (6),

Chem.

[0008] According to the unsaturated carbon-containing thermosetting resin described in the previous paragraph, Y may have the structure shown in formula (7).

Chem.

[0009] According to another aspect of the present invention, there is provided a method for preparing an unsaturated carbon-containing thermosetting resin, comprising the steps of: providing a polymer solution containing a polyphenylene ether compound, a phenol compound, a maleimide compound and a first solvent; subjecting the polymer solution and an alkaline solution to a preliminary polymerization reaction at a preliminary polymerization reaction temperature for a preliminary polymerization reaction time to form a preliminary polymer solution; and subjecting the preliminary polymer solution, a benzene compound solution and a styrene compound solution to a polymerization reaction at a polymerization reaction temperature for a polymerization reaction time to form a polymer solution containing the unsaturated carbon-containing thermosetting resin described in the previous paragraph.

[0010] According to the method for preparing an unsaturated carbon-containing thermosetting resin described in the previous paragraph, the phenol compound may be a bisphenol A derivative.

[0011] According to the method for preparing an unsaturated carbon-containing thermosetting resin described in the previous paragraph, the prepolymerization reaction temperature may be 35°C to 65°C, and the prepolymerization reaction time may be 3 hours to 7 hours.

[0012] According to the method for preparing unsaturated carbon-containing thermosetting resins described in the previous paragraph, the prepolymerization reaction may be carried out in an environment with a pH of 7.5 to 10.5.

[0013] According to the method for preparing an unsaturated carbon-containing thermosetting resin described in the previous paragraph, the benzene compound solution may contain a benzene compound selected from the group consisting of 1,3-bis(trichloromethyl)benzene, 1,4-bis(trichloromethyl)benzene, 1,4-bis(chloromethyl)benzene, 2,4-bis(chloromethyl)trimethylbenzene, and 4,4'-bis(chloromethyl)biphenyl.

[0014] According to the method for preparing an unsaturated carbon-containing thermosetting resin described in the previous paragraph, the styrene compound solution may contain a styrene compound that is 2-chloromethylstyrene, 3-chloromethylstyrene, or 4-chloromethylstyrene.

[0015] According to the method for preparing an unsaturated carbon-containing thermosetting resin described in the previous paragraph, the polymerization reaction temperature may be 35°C to 65°C, and the polymerization reaction time may be 12 hours to 18 hours. [Brief explanation of the drawing]

[0016] The following explanation of the attached drawings is intended to make the above and other objectives, features, advantages, and embodiments of the present invention clearer and easier to understand. [Figure 1] A flowchart of a process for preparing an unsaturated carbon-containing thermosetting resin according to another aspect of the present invention is shown. [Figure 2]The infrared spectra of Example 4, Comparative Example 1, BMI-H, and SA90 are shown. [Modes for carrying out the invention]

[0017] Several embodiments of the present invention will be described below with reference to the drawings, and many practical details will be described in the following description for clarity. However, the reader should understand that these practical details are not intended to limit the present invention. In other words, in some embodiments of the present invention, these practical details are not necessary. Also, in order to simplify the drawings, some conventional structures and elements are shown simply and schematically in the drawings. Duplicate elements may be indicated by the same number.

[0018] <Unsaturated carbon-containing thermosetting resin>

[0019] The unsaturated carbon-containing thermosetting resin of the present invention has the structure shown in the following formula (1), [ka] X is -CH2-, -CH(CH3)-, or -C(CH3)2-, R1, R2, R3, R4, R5, R6, R7, and R8 are each independently a hydrogen atom or a C1-C3 hydrocarbon, a and b are each independently a numerical value between 2 and 500, Y is the structure shown in formula (2), and c and d are each independently a numerical value between 1 and 300. [ka] R9 is C4-C 20 It is a hydrocarbon, where E is the structure shown in formula (3), F is the structure shown in formula (4), and e and f are each independent numerical values ​​from 1 to 200. [ka] R 10 These are C2-C6 straight-chain or branched-chain hydrocarbons, [ka] Z has the structure shown in equation (5). [ka]

[0020] Preferably, Y may have the structure of equation (6), [ka] R 15 It is a C1-C3 hydrocarbon, and R 11 , R 12 , R 18 , R 19 Each of these is independently a C1-C5 hydrocarbon, and R 13 , R 14 , R 16 , R 17 Each of these is independently a hydrogen atom or a C1-C3 hydrocarbon. This allows the molecular chain segments of the unsaturated carbon-containing thermosetting resin of the present invention to have a rigid structure, thereby providing good mechanical strength.

[0021] Preferably, Y may have the structure of equation (7), [ka] This makes it possible to give the molecular chain segments of the unsaturated carbon-containing thermosetting resin of the present invention a rigid and planar structure, providing good mechanical strength. Furthermore, because of its good molecular symmetry and low polarity, it is advantageous for subsequent application to high-frequency printed circuit boards with low dielectric loss (Df).

[0022] Please refer to Figure 1, which shows a step flowchart of a method 100 for preparing an unsaturated carbon-containing thermosetting resin according to another aspect of the present invention, the method 100 for preparing an unsaturated carbon-containing thermosetting resin comprising step 110, step 120, and step 130.

[0023] Step 110 provides a polymer solution comprising a polyphenylene ether compound, a phenol compound, a maleinimide compound, and a first solvent, the first solvent of which may be dimethylacetamide (DMAc). The phenol compound may be a bisphenol A derivative. A bisphenol A derivative is a compound obtained from bisphenol A. For example, the bisphenol A derivative may be 2,2-diallylbisphenol A.

[0024] Step 120 is a prepolymerization reaction step in which a polymer solution and an alkaline solution are prepolymerized at the prepolymerization reaction temperature for a prepolymerization reaction time to form a prepolymer solution. The prepolymerization reaction temperature may be 35°C to 65°C, the pH value range may be 7.5 to 10.5, and the prepolymerization reaction time may be 3 hours to 7 hours to obtain a prepolymer solution. The alkaline solution may be a potassium hydroxide (KOH) solution.

[0025] Step 130 is a polymerization reaction step in which a prepolymer solution, a benzene compound solution, and a styrene compound solution are polymerized at the polymerization reaction temperature for a polymerization reaction time to form a polymer solution containing an unsaturated carbon-containing thermosetting resin. The polymerization reaction temperature may be 35°C to 65°C, and the polymerization reaction time may be 12 hours to 18 hours. The benzene compound solution may contain a benzene compound selected from the group consisting of 1,3-bis(trichloromethyl)benzene, 1,4-bis(trichloromethyl)benzene, 1,4-bis(chloromethyl)benzene, 2,4-bis(chloromethyl)-1,3,5-trimethylbenzene, and 4,4'-bis(chloromethyl)biphenyl. The styrene compound solution contains a styrene compound which may be 2-(Chloromethyl)styrene, 3-(Chloromethyl)styrene, or 4-(Chloromethyl)styrene.

[0026] The following specific embodiments are provided to further illustrate the present invention and to enable those skilled in the art to fully utilize and practice it without requiring excessive interpretation. These embodiments should not be considered limitations on the scope of the present invention, but are used to illustrate how the materials and methods of the present invention are carried out.

[0027] <Example 1>

[0028] NORYL weighing 90±5kg TMA polyphenylene ether compound, SA90 (a patented structure of Sabic, hereinafter abbreviated as SA90), and 3.2 ± 0.3 kg of a bisphenol A derivative were dissolved in 280 ± 20 kg of dimethylacetamide and then added to a reaction vessel. The reaction vessel was equipped with a feed pipe, a stirring blade, a thermometer, and a pH meter, and a heating pack was provided outside the reaction vessel to adjust the temperature inside. The stirring blade may be activated to homogenize the solution in the reaction vessel, and the solution in the reaction vessel may be stirred continuously for 0.5 to 1.5 hours. Then, 5 ± 1.5 kg of a maleinimide compound, Bismaleimide-H (hereinafter abbreviated as BMI-H), may be added from the feed pipe to form a polymer solution, and the liquid in the reaction vessel may be stirred continuously for 1 to 2.5 hours.

[0029] 7.4 ± 1.5 kg of potassium hydroxide solution was added to the reaction vessel through a supply pipe, the temperature range in the reaction vessel was adjusted to 35°C to 65°C, and the pH range may be 7.5 to 10.5. At the same time, the solution in the reaction vessel was stirred, and after a preliminary polymerization reaction for 3 to 7 hours, a preliminary polymer solution was formed.

[0030] 2.4 ± 0.15 kg of benzene compound solution and 16.5 ± 1.5 kg of styrene compound solution are added to the reaction vessel from the supply pipe, the temperature range in the reaction vessel is adjusted to 35°C to 65°C, and the solutions in the reaction vessel are simultaneously stirred. After polymerization reaction for 12 to 18 hours, a polymer solution containing an unsaturated carbon-containing thermosetting resin is formed, and the unsaturated carbon-containing thermosetting resin of Example 1 (hereinafter abbreviated as Example 1) having the structure shown in formula (1) can be obtained. [ka] X is -C(CH3)2-, R1, R2, R7, and R8 are each independently -CH3, R3, R4, R5, and R6 are each independently hydrogen atoms, a and b are each independently numerical values ​​from 2 to 35, Y is the structure shown in formula (7), and c and d are each independently numerical values ​​from 1 to 4. [ka] E is the structure shown in equation (3), F is the structure shown in equation (4), and e and f are each independent numerical values ​​from 1 to 6. [ka] R 10 It is -C(CH3)2-, [ka] Z has the structure shown in equation (5). [ka]

[0031] <Example 2>

[0032] The unsaturated carbon-containing thermosetting resin of Example 2 (hereinafter referred to as Example 2) was manufactured using a preparation method similar to that of Example 1 and has a similar structure to that of Example 1. However, it differs in that the amount of BMI-H added during the preparation of Example 2 was 11 ± 1.5 kg, while other preparation conditions were the same as those of Example 1.

[0033] <Example 3>

[0034] The unsaturated carbon-containing thermosetting resin of Example 3 (hereinafter referred to as Example 3) was manufactured using a preparation method similar to that of Example 1 and has a similar structure to that of Example 1. However, it differs in that the amount of BMI-H added during the preparation of Example 3 was 17 ± 1.5 kg, and all other preparation conditions were the same as those of Example 1.

[0035] <Example 4>

[0036] The unsaturated carbon-containing thermosetting resin of Example 4 (hereinafter referred to as Example 4) was manufactured using a preparation method similar to that of Example 1 and has a similar structure to that of Example 1. However, it differs in that the amount of BMI-H added during the preparation of Example 4 was 23 ± 1.5 kg, and all other preparation conditions were the same as those of Example 1.

[0037] <Example 5>

[0038] The unsaturated carbon-containing thermosetting resin of Example 5 (hereinafter referred to as Example 5) was manufactured using a preparation method similar to that of Example 1 and has a similar structure to that of Example 1. However, it differs in that the amount of BMI-H added during the preparation of Example 5 was 29 ± 1.5 kg, and all other preparation conditions were the same as those of Example 1.

[0039] <Comparative Example 1>

[0040] The unsaturated carbon-containing thermosetting resin of Comparative Example 1 (hereinafter referred to as Comparative Example 1) is manufactured using a preparation method similar to that of Example 1, but unlike Comparative Example 1, BMI-H is not added when preparing Comparative Example 1, and Comparative Example 1 has the structure shown in formula (8). [ka] X is -C(CH3)2-, R1, R2, R7, and R8 are each independently -CH3, R3, R4, R5, and R6 are each independently hydrogen atoms, a and b are each independently numerical values ​​from 2 to 35, E is the structure shown in formula (3), F is the structure shown in formula (4), and e and f are each independently numerical values ​​from 1 to 6. [ka] R 10 It is -C(CH3)2-, [ka] Z has the structure shown in equation (5). [ka]

[0041] <Infrared Spectrum (IR)>

[0042] Please refer to Figure 2, which shows the infrared spectra of Example 4, Comparative Example 1, BMI-H, and SA90. Example 4 is an unsaturated carbon-containing thermosetting resin containing a maleimide structure, while Comparative Example 1 is an unsaturated carbon-containing thermosetting resin that does not contain a maleimide structure. Compared to Comparative Example 1, the infrared spectrum of Example 4 shows a higher 1710 cm⁻¹. ‐1 The characteristic peak of the C=O double bond of the amide group observed was the same as the characteristic peak of BMI-H, indicating that the unsaturated carbon-containing thermosetting resin of the present invention has a maleimide graft structure on the polymer chain of SA90.

[0043] <Gel permeation chromatography (GPC)>

[0044] The weight-average molecular weight (Mw) of Examples 1 to 5 and Comparative Example 1 was analyzed by gel permeation chromatography, and the measurement results are listed in Table 1 below. Examples 1 to 5 were unsaturated carbon-containing thermosetting resins containing maleinimide structures, while Comparative Example 1 was an unsaturated carbon-containing thermosetting resin without maleinimide structures. As can be seen from Table 1, compared to Comparative Example 1, the unsaturated carbon-containing thermosetting resins of Examples 1 to 5 of the present invention had a higher weight-average molecular weight because they had maleinimide structures grafted onto the SA90 polymer chain. Furthermore, the maleinimide structure on the polymer chain provided a rigid molecular structure, which further improved the mechanical properties of the material. [Table 1]

[0045] <Thermal properties evaluation>

[0046] For Examples 1 to 5 and Comparative Example 1, the glass transition temperature (Tg) was measured using a differential scanning calorimeter (DSC), and the measurement results are shown in Table 2 below to evaluate the thermal properties. The DSC heating conditions were as follows: the temperature was raised once at a heating rate of 20°C / min from 50°C to 350°C, then cooled from 350°C to 50°C at a cooling rate of 80°C / min, the temperature was maintained at 50°C for 2 minutes, and then the temperature was raised a second time at a heating rate of 20°C / min from 50°C to 350°C.

[0047] Please refer to Table 2, which shows the glass transition temperature data for Examples 1 to 5 and Comparative Example 1. As can be seen from Table 2, Examples 1 to 5 of the present invention have higher glass transition temperatures compared to Comparative Example 1. This is because the maleinimide structure on the polymer chain is planar, facilitating the arrangement between polymer chains, and further increasing the glass transition temperature of the unsaturated carbon-containing thermosetting resin. This indicates that the unsaturated carbon-containing thermosetting resin of the present invention has good thermal stability. [Table 2]

[0048] <Preparing the gel recipe>

[0049] Gel recipes were prepared for Examples 1 to 5 and Comparative Example 1 to evaluate the thermal stability of the products of unsaturated carbon-containing thermosetting resins used in the gel process for printed circuit boards. The gel recipe preparation process included the following: 100 ± 2 g each of Examples 1 to 5 and Comparative Example 1 were added to 110 ± 5 g of methyl ethyl ketone (MEK), and 67 ± 1 g of triallyl isocyanurate (TAIC) as a crosslinking agent was added to each, and the mixture was stirred at room temperature until the solid was completely dissolved. 10 ± 0.5 g of an initiator containing 10 wt% dicumyl peroxide (DCP) and methyl ethyl ketone was added to each to obtain the respective gel recipes. The gel process was carried out at 170 ± 1.5°C using the gel recipe produced in Example 1, and the resulting cured product was Example 6 (hereinafter abbreviated as Example 6). Example 7 (hereinafter abbreviated as Example 7) was produced using Example 2 instead of Example 1, and a preparation method similar to that of Example 6. Example 8 (hereinafter abbreviated as Example 8) was produced using Example 3 instead of Example 1, and a preparation method similar to that of Example 6. Example 9 (hereinafter abbreviated as Example 9) was produced using Example 4 instead of Example 1, and a preparation method similar to that of Example 6. Example 10 (hereinafter abbreviated as Example 10) was produced using Example 5 instead of Example 1, and a preparation method similar to that of Example 6. Comparative Example 2 (hereinafter abbreviated as Comparative Example 2) was produced using Comparative Example 1 instead of Example 1, and a preparation method similar to that of Example 6.

[0050] <Evaluation of the thermal properties of cured products>

[0051] For Examples 6 to 10 and Comparative Example 2, the glass transition temperature (Tg) was measured using a differential scanning calorimeter (DSC), and the thermal properties were evaluated based on the measurement results shown in Table 3 below. The DSC heating conditions were as follows: the temperature was raised once at a heating rate of 20°C / min from 50°C to 350°C, then cooled from 350°C to 50°C at a cooling rate of 80°C / min, the temperature was maintained at 50°C for 2 minutes, and then the temperature was raised a second time at a heating rate of 20°C / min from 50°C to 350°C.

[0052] Please refer to Table 3, which contains the glass transition temperature data for Examples 6 to 10 and Comparative Example 2. As can be seen from Table 3, Examples 6 to 10 had higher glass transition temperatures and better thermal stability compared to Comparative Example 2. Therefore, using the unsaturated carbon-containing thermosetting resin of the present invention in the printed circuit board process contributes to the production stability of the printed circuit board process. [Table 3]

[0053] In summary, the unsaturated carbon-containing thermosetting resin of the present invention is easy to synthesize and mass-produce, has a good rigid structure and a high glass transition temperature, and when used as a printed circuit board substrate, it can contribute to obtaining a printed circuit board substrate with excellent mechanical strength and thermal stability.

[0054] Although the present invention is disclosed in the embodiments described above, these are not intended to limit the invention, and any person skilled in the art can make various modifications and finishes without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention is the same as that specified in the scope of the patent application appended later. [Explanation of symbols]

[0055] 100: Method for preparing unsaturated carbon-containing thermosetting resins 110, 120, 130: Process

Claims

1. Having the structure shown in the following formula (1), 【Chemistry 1】 X is -CH ２ -, -CH(CH ３ )-or-C(CH ３ ) ２ - and R １ , R ２ , R ３ , R ４ , R ５ , R ６ , R ７ and R ８ are each independently a hydrogen atom or a C １ -C ３ hydrocarbon, and a and b are each independently numerical values from 2 to 500. Y is the structure shown in equation (2), and c and d are each independent numerical values ​​from 1 to 300. 【Chemistry 2】 R ９ C ４ -C ２０ It is a hydrocarbon, E is the structure shown in formula (3), F is the structure shown in formula (4), and e and f are each independent numerical values ​​from 1 to 200. 【Transformation 3】 R １０ C ２ -C ６ It is a straight-chain or branched-chain hydrocarbon, 【Chemistry 4】 Z is an unsaturated carbon-containing thermosetting resin having the structure shown in formula (5). 【Transformation 5】

2. Y has the structure shown in equation (6), 【Transformation 6】 R １５ C １ -C ３ It is a hydrocarbon, R １１ , R １２ , R １８ and R １９ Each of them is independently C １ -C ５ It is a hydrocarbon, R １３ , R １４ , R １６ and R １７ Each of these is independently a hydrogen atom or C １ -C ３ The unsaturated carbon-containing thermosetting resin according to claim 1, which is a hydrocarbon.

3. The unsaturated carbon-containing thermosetting resin according to claim 1, wherein Y has the structure shown in formula (7). 【Transformation 7】

4. A step of providing a polymer solution containing a polyphenylene ether compound, a phenol compound, a maleinimide compound, and a first solvent, The process involves prepolymerizing the polymer solution and the alkaline solution at the prepolymerization reaction temperature for a prepolymerization reaction time to form a prepolymer solution. The steps include: polymerizing the aforementioned pre-polymer solution, benzene compound solution, and styrene compound solution at the polymerization reaction temperature for the polymerization reaction time to form a polymer solution containing the unsaturated carbon-containing thermosetting resin; A method for preparing an unsaturated carbon-containing thermosetting resin according to claim 1, comprising:

5. The method for preparing an unsaturated carbon-containing thermosetting resin according to claim 4, wherein the phenol compound is a bisphenol A derivative.

6. The method for preparing an unsaturated carbon-containing thermosetting resin according to claim 4, wherein the prepolymerization reaction temperature is 35°C to 65°C, and the prepolymerization reaction time is 3 hours to 7 hours.

7. The method for preparing an unsaturated carbon-containing thermosetting resin according to claim 4, wherein the prepolymerization reaction is carried out in an environment with a pH of 7.5 to 10.

5.

8. The method for preparing an unsaturated carbon-containing thermosetting resin according to claim 4, wherein the benzene compound solution comprises a benzene compound selected from the group consisting of 1,3-bis(trichloromethyl)benzene, 1,4-bis(trichloromethyl)benzene, 1,4-bis(chloromethyl)benzene, 2,4-bis(chloromethyl)trimethylbenzene, and 4,4'-bis(chloromethyl)biphenyl.

9. The method for preparing an unsaturated carbon-containing thermosetting resin according to claim 4, wherein the styrene compound solution comprises a styrene compound which is 2-chloromethylstyrene, 3-chloromethylstyrene, or 4-chloromethylstyrene.

10. The method for preparing an unsaturated carbon-containing thermosetting resin according to claim 4, wherein the polymerization reaction temperature is 35°C to 65°C and the polymerization reaction time is 12 hours to 18 hours.

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