Can I divorce a co-founder

You can try to buy them out. Depending on what type of agreement is in place (what do you mean you don't have a shareholders agreement?) the method, price, and structure of such a buyout would be determined.

However, bear in mind that there are 2 major issues raised in your question, though you only ask about one of them. The one you ask about, getting rid of a co-founder, is only half the problem. The other half is that you've indicated there's a clear split between sales and technical.

There are multiple possible causes for this split. One, as you've indicated, is that the two groups have differing loyalties, and so it would not be possible for these two groups to resolve those differences.

The other, as pointed out in comments on the question, is that the technical team either knows something the sales team does not, or the two teams are not communicating with one another effectively. Either way, the resolution would revolve not around getting a new technical team (or a new sales team, for that matter) as the new pairing would result in the same issue down the line.

You may be better off getting someone to come in and mediate between the teams, to first ensure that the two teams do understand one another, and the expectations of each team is reasonable and possible. Only if that's determined to be the case, and the issue is of differing priorities and loyalties, should a split up be considered.

Addendum

In response to the addition to the question:

1. Scaling a team quickly is usually a bad idea - without sufficient time to figure out both the qualifications of candidates and the chemistry with the existing team, this can rapidly backfire. You can still hire aggressively, but the reasons you cite for being slower and more careful are valid.
2. As you pointed out, without the developers, your business would be in trouble. That in turn means that you have to work things out with them. If you can't do it on your own, bring in a mediator to help work things out.

The short answer is there is a way to divorce but it would fall to the articles of organization and to the laws of where the business was organized in. There will need to be an attorney and if an amicable agreement isn't completed it could be quite costly.

The positives that I read in what is posted is there is interest in what is being offered by those that have money but doing. So I suggest ask what is it that got them interested in the funding? Was there anything about the mock ups, intellectual property, technical members or any design pieces that attracted the first investments?

What can two sales guys be doing this early on? Is the product/service already being sold? Do they have a marketing plan, focus groups, contacts in businesses? The early work for a firm that is doing something in technology is typically strongly technical with some marketing type of feedback. Really product development type of stuff. What is it that the sales guys adding to this part of the process? What do they understand of it? There are real risks that the golden egg maybe in the technical team and that the sales people have gotten over emphasized.

So I suggest reviewing what is it that is causing the break? Is the disagreement on features and functions is it a disagreement on tools? Or is it a disagreement on how it will be sold? So likely you have some type of business plan and in it there is a description of the product/service along with who will buy it and how big that market is and how it can be marketed and sold to them. In that there are assumptions that need to be validated that describe how this will be met. Developers are typically persuaded by numbers. I suggest showing what needs to be achieved and what that will mean by the numbers.

Good luck

Because of generation gap, difference in background, sales reps idea won't match with technical founder.

[flame suit on]

At best, this sounds like rationalization... at worse age discrimination. And I'm not part of the 20 something club.

Everyone can have an "idea" - the problem comes from determining whether the idea will produce busy work or materially improve the companies objectives.

If the justification is that "because we are sales guys" or "because we are tech and know better" then you are at an impasse and will never move forward. If neither group understands or appreciates the work that goes into performing the task, they both will underestimate the magnitude of the task - further exasperating the problem.

And "simply divorcing and recreating" is a cop out - it assumes that development is simply something that you purchase. What about the domain knowledge gained from building and facing your customer base?

I would take a hard look at the company culture and determine where the communication problem is - and attempt to fix this first.

First problem: Why would someone from a sales position push the agenda of hiring more developers as a solution? Shouldn't the discussion revolve around what the business goal is, and than let the technical part of the company weigh in with their recommendation on how to achieve the goal? Consider the reverse - I doubt one would feel that adding 10 more sales people to improve deal flow under the auspices that the current staff is incapable of meeting objectives wouldn't be warmly received either.

Planning and product development should be a collaborative effort - not a "push the features under the door and wait for a response". In addition, a tech founder can't just be a lead developer - yes, coding is important - but also address many of the tasks typically reserved to a CTO (here is a good article that talks about the founder developer gap).

Some collaborative product / customer development methodologies could also help you mend the "us vs them" chasm and refocus toward delivering value to your customer base. Search this board for some Agile / Lean recommendations - they may offer some additional ideas. Or bring in a advisor who is technical to help.

Best of luck with your efforts.